{
  "index": "1951-A-4",
  "type": "ANA",
  "tag": [
    "ANA",
    "ALG"
  ],
  "difficulty": "",
  "question": "\\begin{array}{l}\n\\text { 4. Trace the curve whose equation is: }\\\\\ny^{4}-x^{4}-96 y^{2}+100 x^{2}=0\n\\end{array}",
  "solution": "Solution. On completing squares we obtain\n\\[\n\\left(x^{2}-50\\right)^{2}-\\left(y^{2}-48\\right)^{2}=14^{2}\n\\]\n\nLetting \\( X=x^{2}, Y=y^{2} \\), we find\n\\[\n(X-50)^{2}-(Y-48)^{2}=14^{2}\n\\]\nand the graph of this equation in the \\( X Y \\)-plane is readily identified as a rectangular hyperbola with center at \\( (50,48) \\) and asymptotes\n\\[\n\\left\\{\\begin{array}{l}\nX+Y=98 \\\\\nX-Y=2 .\n\\end{array}\\right.\n\\]\n\nIn the present situation interest is confined to the first quadrant of the \\( X Y \\)-plane. For each point ( \\( X, Y \\) ) in the first quadrant there are four points of the required locus \\( L \\), namely \\( ( \\pm \\sqrt{X}, \\pm \\sqrt{Y}) \\). Because the transformation \\( (x, y) \\mapsto(X, Y) \\) mapping each quadrant of the \\( x y \\)-plane onto the first quadrant of the \\( X Y \\)-plane is differentiable in both directions, the smooth arcs of the auxiliary graph correspond to smooth arcs of \\( L \\).\nThe three points \\( (0,0),(0,96) \\), and \\( (100,0) \\) of the auxiliary graph lying on the boundary of the first quadrant correspond to five points ( 0,0 ), ( \\( 0, \\pm \\sqrt{96} \\) ), \\( ( \\pm 10,0) \\) of \\( L \\) which require special consideration.\nThe function\n\\[\nf(x, y)=y^{4}-x^{4}-96 y^{2}+100 x^{2}\n\\]\nhas gradient\n\\[\n\\nabla f=\\left(-4 x^{3}+200 x, 4 y^{3}-192 y\\right) .\n\\]\n\nSince \\( \\nabla f \\) does not vanish at the points \\( (0, \\pm \\sqrt{96}),( \\pm 10,0) \\), the curve \\( L \\) is smooth at those points. The first component of \\( \\nabla f \\) vanishes at \\( (0, \\pm \\sqrt{96}) \\), so \\( L \\) has horizontal tangents at these two points. The second component of \\( \\nabla f \\) vanishes at \\( ( \\pm 10,0) \\), so \\( L \\) has vertical tangents at these points. At the origin, both components of \\( \\nabla f \\) vanish, so we consider the quadratic terms\n\\[\n100 x^{2}-96 y^{2}\n\\]\nof \\( f \\) at this point. Since these constitute a non-degenerate quadratic form which vanishes along the lines \\( y= \\pm(100 / 96) x \\), the curve \\( L \\) crosses itself at the origin, the two branches being tangent to these two lines.\n\nExamination shows that the first component of \\( \\nabla f \\) does not vanish at any other points of \\( L \\), so \\( L \\) has no more horizontal tangents, but the second component of \\( \\nabla f \\) vanishes at eight more points of \\( L \\), namely \\( ( \\pm 6, \\pm \\sqrt{48}),( \\pm 8, \\pm \\sqrt{48}) \\), so \\( L \\) has vertical tangents at these points, corresponding to the vertical tangents on the auxiliary graph.\n\nSince the line \\( X-Y=2 \\) is an asymptote to the auxiliary hyperbola, \\( X-Y \\rightarrow 2 \\) along the unbounded arc of this hyperbola in the first quadrant. Correspondingly,\n\\[\nx-y=\\sqrt{X}-\\sqrt{Y}=\\frac{X-Y}{\\sqrt{X}+\\sqrt{Y}} \\rightarrow 0\n\\]\nalong the unbounded arc of \\( L \\) in the first quadrant. Hence \\( L \\) is asymptotic to the line \\( y=x \\) in the first quadrant. By symmetry \\( L \\) is asymptotic to the same line in the third quadrant and to \\( y=-x \\) in the second and fourth quadrants.\nSince there are no points of the auxiliary locus in the strip \\( 36<X<64 \\), there are no points of \\( L \\) in the strips \\( 6<x<8 \\) and \\( -8<x<-6 \\).\n\nThe graph of \\( f(x, y)=0 \\) is therefore as shown.\nFor general methods of graphing higher-degree plane curves, see C. A. Stewart, Advanced Calculus, 3rd ed., Methuen, London, 1951, or J. H.",
  "vars": [
    "x",
    "y",
    "X",
    "Y"
  ],
  "params": [
    "f",
    "\\\\nabla",
    "L"
  ],
  "sci_consts": [],
  "variants": {
    "descriptive_long": {
      "map": {
        "x": "abscissa",
        "y": "ordinate",
        "X": "squaredx",
        "Y": "squaredy",
        "f": "quarticfn",
        "\\nabla": "gradient",
        "L": "resultantcurve"
      },
      "question": "\\begin{array}{l}\n\\text { 4. Trace the curve whose equation is: }\\\\\nordinate^{4}-abscissa^{4}-96\\,ordinate^{2}+100\\,abscissa^{2}=0\n\\end{array}",
      "solution": "Solution. On completing squares we obtain\n\\[\n\\left(abscissa^{2}-50\\right)^{2}-\\left(ordinate^{2}-48\\right)^{2}=14^{2}\n\\]\n\nLetting \\( squaredx=abscissa^{2},\\; squaredy=ordinate^{2} \\), we find\n\\[\n(squaredx-50)^{2}-(squaredy-48)^{2}=14^{2}\n\\]\nand the graph of this equation in the \\( squaredx\\; squaredy \\)-plane is readily identified as a rectangular hyperbola with center at \\( (50,48) \\) and asymptotes\n\\[\n\\left\\{\\begin{array}{l}\nsquaredx+squaredy=98 \\\\\nsquaredx-squaredy=2 .\n\\end{array}\\right.\n\\]\n\nIn the present situation interest is confined to the first quadrant of the \\( squaredx\\; squaredy \\)-plane. For each point \\( (squaredx, squaredy) \\) in the first quadrant there are four points of the required locus \\( resultantcurve \\), namely \\( (\\pm\\sqrt{squaredx}, \\pm\\sqrt{squaredy}) \\). Because the transformation \\( (abscissa,\\, ordinate) \\mapsto(squaredx,\\, squaredy) \\) mapping each quadrant of the \\( abscissa\\, ordinate\\)-plane onto the first quadrant of the \\( squaredx\\, squaredy\\)-plane is differentiable in both directions, the smooth arcs of the auxiliary graph correspond to smooth arcs of \\( resultantcurve \\).\nThe three points \\( (0,0),(0,96) \\), and \\( (100,0) \\) of the auxiliary graph lying on the boundary of the first quadrant correspond to five points \\( (0,0),\\; (0, \\pm \\sqrt{96}),\\; (\\pm 10,0) \\) of \\( resultantcurve \\) which require special consideration.\nThe function\n\\[\nquarticfn(abscissa,\\, ordinate)=ordinate^{4}-abscissa^{4}-96\\,ordinate^{2}+100\\,abscissa^{2}\n\\]\nhas gradient\n\\[\ngradient\\, quarticfn=\\left(-4\\,abscissa^{3}+200\\,abscissa,\\; 4\\,ordinate^{3}-192\\,ordinate\\right) .\n\\]\n\nSince \\( gradient\\, quarticfn \\) does not vanish at the points \\( (0, \\pm \\sqrt{96}),(\\pm 10,0) \\), the curve \\( resultantcurve \\) is smooth at those points. The first component of \\( gradient\\, quarticfn \\) vanishes at \\( (0, \\pm \\sqrt{96}) \\), so \\( resultantcurve \\) has horizontal tangents at these two points. The second component of \\( gradient\\, quarticfn \\) vanishes at \\( (\\pm 10,0) \\), so \\( resultantcurve \\) has vertical tangents at these points. At the origin, both components of \\( gradient\\, quarticfn \\) vanish, so we consider the quadratic terms\n\\[\n100\\,abscissa^{2}-96\\,ordinate^{2}\n\\]\nof \\( quarticfn \\) at this point. Since these constitute a non-degenerate quadratic form which vanishes along the lines \\( ordinate=\\pm(100/96)\\,abscissa \\), the curve \\( resultantcurve \\) crosses itself at the origin, the two branches being tangent to these two lines.\n\nExamination shows that the first component of \\( gradient\\, quarticfn \\) does not vanish at any other points of \\( resultantcurve \\), so \\( resultantcurve \\) has no more horizontal tangents, but the second component of \\( gradient\\, quarticfn \\) vanishes at eight more points of \\( resultantcurve \\), namely \\( (\\pm 6, \\pm \\sqrt{48}),(\\pm 8, \\pm \\sqrt{48}) \\), so \\( resultantcurve \\) has vertical tangents at these points, corresponding to the vertical tangents on the auxiliary graph.\n\nSince the line \\( squaredx-squaredy=2 \\) is an asymptote to the auxiliary hyperbola, \\( squaredx-squaredy \\rightarrow 2 \\) along the unbounded arc of this hyperbola in the first quadrant. Correspondingly,\n\\[\nabscissa-ordinate=\\sqrt{squaredx}-\\sqrt{squaredy}=\\frac{squaredx-squaredy}{\\sqrt{squaredx}+\\sqrt{squaredy}} \\rightarrow 0\n\\]\nalong the unbounded arc of \\( resultantcurve \\) in the first quadrant. Hence \\( resultantcurve \\) is asymptotic to the line \\( ordinate=abscissa \\) in the first quadrant. By symmetry \\( resultantcurve \\) is asymptotic to the same line in the third quadrant and to \\( ordinate=-abscissa \\) in the second and fourth quadrants.\nSince there are no points of the auxiliary locus in the strip \\( 36<squaredx<64 \\), there are no points of \\( resultantcurve \\) in the strips \\( 6<abscissa<8 \\) and \\( -8<abscissa<-6 \\).\n\nThe graph of \\( quarticfn(abscissa,\\, ordinate)=0 \\) is therefore as shown.\nFor general methods of graphing higher-degree plane curves, see C. A. Stewart, Advanced Calculus, 3rd ed., Methuen, London, 1951, or J. H."
    },
    "descriptive_long_confusing": {
      "map": {
        "x": "waterfall",
        "y": "driftwood",
        "X": "moonlight",
        "Y": "sandstorm",
        "f": "riverbank",
        "\\nabla": "thunderbolt",
        "L": "oceanbreeze"
      },
      "question": "\\begin{array}{l}\n\\text { 4. Trace the curve whose equation is: }\\\\\ndriftwood^{4}-waterfall^{4}-96 driftwood^{2}+100 waterfall^{2}=0\n\\end{array}",
      "solution": "Solution. On completing squares we obtain\n\\[\n\\left(waterfall^{2}-50\\right)^{2}-\\left(driftwood^{2}-48\\right)^{2}=14^{2}\n\\]\n\nLetting \\( moonlight=waterfall^{2}, sandstorm=driftwood^{2} \\), we find\n\\[\n(moonlight-50)^{2}-(sandstorm-48)^{2}=14^{2}\n\\]\nand the graph of this equation in the \\( moonlight sandstorm \\)-plane is readily identified as a rectangular hyperbola with center at \\( (50,48) \\) and asymptotes\n\\[\n\\left\\{\\begin{array}{l}\nmoonlight+sandstorm=98 \\\\\nmoonlight-sandstorm=2 .\n\\end{array}\\right.\n\\]\n\nIn the present situation interest is confined to the first quadrant of the \\( moonlight sandstorm \\)-plane. For each point ( \\( moonlight, sandstorm \\) ) in the first quadrant there are four points of the required locus \\( oceanbreeze \\), namely \\( ( \\pm \\sqrt{moonlight}, \\pm \\sqrt{sandstorm}) \\). Because the transformation \\( (waterfall, driftwood) \\mapsto(moonlight, sandstorm) \\) mapping each quadrant of the \\( waterfall driftwood \\)-plane onto the first quadrant of the \\( moonlight sandstorm \\)-plane is differentiable in both directions, the smooth arcs of the auxiliary graph correspond to smooth arcs of \\( oceanbreeze \\).\nThe three points \\( (0,0),(0,96) \\), and \\( (100,0) \\) of the auxiliary graph lying on the boundary of the first quadrant correspond to five points ( 0,0 ), ( \\( 0, \\pm \\sqrt{96} \\) ), \\( ( \\pm 10,0) \\) of \\( oceanbreeze \\) which require special consideration.\nThe function\n\\[\nriverbank(waterfall, driftwood)=driftwood^{4}-waterfall^{4}-96 driftwood^{2}+100 waterfall^{2}\n\\]\nhas gradient\n\\[\nthunderbolt riverbank=\\left(-4 waterfall^{3}+200 waterfall, 4 driftwood^{3}-192 driftwood\\right) .\n\\]\n\nSince \\( thunderbolt riverbank \\) does not vanish at the points \\( (0, \\pm \\sqrt{96}),( \\pm 10,0) \\), the curve \\( oceanbreeze \\) is smooth at those points. The first component of \\( thunderbolt riverbank \\) vanishes at \\( (0, \\pm \\sqrt{96}) \\), so \\( oceanbreeze \\) has horizontal tangents at these two points. The second component of \\( thunderbolt riverbank \\) vanishes at \\( ( \\pm 10,0) \\), so \\( oceanbreeze \\) has vertical tangents at these points. At the origin, both components of \\( thunderbolt riverbank \\) vanish, so we consider the quadratic terms\n\\[\n100 waterfall^{2}-96 driftwood^{2}\n\\]\nof \\( riverbank \\) at this point. Since these constitute a non-degenerate quadratic form which vanishes along the lines \\( driftwood= \\pm(100 / 96) waterfall \\), the curve \\( oceanbreeze \\) crosses itself at the origin, the two branches being tangent to these two lines.\n\nExamination shows that the first component of \\( thunderbolt riverbank \\) does not vanish at any other points of \\( oceanbreeze \\), so \\( oceanbreeze \\) has no more horizontal tangents, but the second component of \\( thunderbolt riverbank \\) vanishes at eight more points of \\( oceanbreeze \\), namely \\( ( \\pm 6, \\pm \\sqrt{48}),( \\pm 8, \\pm \\sqrt{48}) \\), so \\( oceanbreeze \\) has vertical tangents at these points, corresponding to the vertical tangents on the auxiliary graph.\n\nSince the line \\( moonlight-sandstorm=2 \\) is an asymptote to the auxiliary hyperbola, \\( moonlight-sandstorm \\rightarrow 2 \\) along the unbounded arc of this hyperbola in the first quadrant. Correspondingly,\n\\[\nwaterfall-driftwood=\\sqrt{moonlight}-\\sqrt{sandstorm}=\\frac{moonlight-sandstorm}{\\sqrt{moonlight}+\\sqrt{sandstorm}} \\rightarrow 0\n\\]\nalong the unbounded arc of \\( oceanbreeze \\) in the first quadrant. Hence \\( oceanbreeze \\) is asymptotic to the line \\( driftwood=waterfall \\) in the first quadrant. By symmetry \\( oceanbreeze \\) is asymptotic to the same line in the third quadrant and to \\( driftwood=-waterfall \\) in the second and fourth quadrants.\nSince there are no points of the auxiliary locus in the strip \\( 36<moonlight<64 \\), there are no points of \\( oceanbreeze \\) in the strips \\( 6<waterfall<8 \\) and \\( -8<waterfall<-6 \\).\n\nThe graph of \\( riverbank(waterfall, driftwood)=0 \\) is therefore as shown.\nFor general methods of graphing higher-degree plane curves, see C. A. Stewart, Advanced Calculus, 3rd ed., Methuen, London, 1951, or J. H."
    },
    "descriptive_long_misleading": {
      "map": {
        "x": "knownvalue",
        "y": "horizontal",
        "X": "rootvalue",
        "Y": "rootheight",
        "f": "constant",
        "\\\\nabla": "integralop",
        "L": "singlepoint"
      },
      "question": "\\begin{array}{l}\n\\text { 4. Trace the curve whose equation is: }\\\\\nhorizontal^{4}-knownvalue^{4}-96 horizontal^{2}+100 knownvalue^{2}=0\n\\end{array}",
      "solution": "Solution. On completing squares we obtain\n\\[\n\\left(knownvalue^{2}-50\\right)^{2}-\\left(horizontal^{2}-48\\right)^{2}=14^{2}\n\\]\n\nLetting \\( rootvalue=knownvalue^{2}, rootheight=horizontal^{2} \\), we find\n\\[\n(rootvalue-50)^{2}-(rootheight-48)^{2}=14^{2}\n\\]\nand the graph of this equation in the \\( rootvalue rootheight \\)-plane is readily identified as a rectangular hyperbola with center at \\( (50,48) \\) and asymptotes\n\\[\n\\left\\{\\begin{array}{l}\nrootvalue+rootheight=98 \\\\\nrootvalue-rootheight=2 .\n\\end{array}\\right.\n\\]\n\nIn the present situation interest is confined to the first quadrant of the \\( rootvalue rootheight \\)-plane. For each point ( \\( rootvalue, rootheight \\) ) in the first quadrant there are four points of the required locus \\( singlepoint \\), namely \\( ( \\pm \\sqrt{rootvalue}, \\pm \\sqrt{rootheight}) \\). Because the transformation \\( (knownvalue, horizontal) \\mapsto(rootvalue, rootheight) \\) mapping each quadrant of the \\( knownvalue horizontal \\)-plane onto the first quadrant of the \\( rootvalue rootheight \\)-plane is differentiable in both directions, the smooth arcs of the auxiliary graph correspond to smooth arcs of \\( singlepoint \\).\nThe three points \\( (0,0),(0,96) \\), and \\( (100,0) \\) of the auxiliary graph lying on the boundary of the first quadrant correspond to five points ( 0,0 ), ( \\( 0, \\pm \\sqrt{96} \\) ), \\( ( \\pm 10,0) \\) of \\( singlepoint \\) which require special consideration.\nThe function\n\\[\nconstant(knownvalue, horizontal)=horizontal^{4}-knownvalue^{4}-96 horizontal^{2}+100 knownvalue^{2}\n\\]\nhas gradient\n\\[\nintegralop constant=\\left(-4 knownvalue^{3}+200 knownvalue, 4 horizontal^{3}-192 horizontal\\right) .\n\\]\n\nSince \\( integralop constant \\) does not vanish at the points \\( (0, \\pm \\sqrt{96}),( \\pm 10,0) \\), the curve \\( singlepoint \\) is smooth at those points. The first component of \\( integralop constant \\) vanishes at \\( (0, \\pm \\sqrt{96}) \\), so \\( singlepoint \\) has horizontal tangents at these two points. The second component of \\( integralop constant \\) vanishes at \\( ( \\pm 10,0) \\), so \\( singlepoint \\) has vertical tangents at these points. At the origin, both components of \\( integralop constant \\) vanish, so we consider the quadratic terms\n\\[\n100 knownvalue^{2}-96 horizontal^{2}\n\\]\nof \\( constant \\) at this point. Since these constitute a non-degenerate quadratic form which vanishes along the lines \\( horizontal= \\pm(100 / 96) knownvalue \\), the curve \\( singlepoint \\) crosses itself at the origin, the two branches being tangent to these two lines.\n\nExamination shows that the first component of \\( integralop constant \\) does not vanish at any other points of \\( singlepoint \\), so \\( singlepoint \\) has no more horizontal tangents, but the second component of \\( integralop constant \\) vanishes at eight more points of \\( singlepoint \\), namely \\( ( \\pm 6, \\pm \\sqrt{48}),( \\pm 8, \\pm \\sqrt{48}) \\), so \\( singlepoint \\) has vertical tangents at these points, corresponding to the vertical tangents on the auxiliary graph.\n\nSince the line \\( rootvalue-rootheight=2 \\) is an asymptote to the auxiliary hyperbola, \\( rootvalue-rootheight \\rightarrow 2 \\) along the unbounded arc of this hyperbola in the first quadrant. Correspondingly,\n\\[\nknownvalue-horizontal=\\sqrt{rootvalue}-\\sqrt{rootheight}=\\frac{rootvalue-rootheight}{\\sqrt{rootvalue}+\\sqrt{rootheight}} \\rightarrow 0\n\\]\nalong the unbounded arc of \\( singlepoint \\) in the first quadrant. Hence \\( singlepoint \\) is asymptotic to the line \\( horizontal=knownvalue \\) in the first quadrant. By symmetry \\( singlepoint \\) is asymptotic to the same line in the third quadrant and to \\( horizontal=-knownvalue \\) in the second and fourth quadrants.\nSince there are no points of the auxiliary locus in the strip \\( 36<rootvalue<64 \\), there are no points of \\( singlepoint \\) in the strips \\( 6<knownvalue<8 \\) and \\( -8<knownvalue<-6 \\).\n\nThe graph of \\( constant(knownvalue, horizontal)=0 \\) is therefore as shown.\nFor general methods of graphing higher-degree plane curves, see C. A. Stewart, Advanced Calculus, 3rd ed., Methuen, London, 1951, or J. H."
    },
    "garbled_string": {
      "map": {
        "x": "qzxwvtnp",
        "y": "hjgrksla",
        "X": "vndkrcema",
        "Y": "plxmoyghi",
        "f": "skdptwre",
        "\\nabla": "ugfjdksa",
        "L": "tonmczahl"
      },
      "question": "\\begin{array}{l}\n\\text { 4. Trace the curve whose equation is: }\\\\\nhjgrksla^{4}-qzxwvtnp^{4}-96 hjgrksla^{2}+100 qzxwvtnp^{2}=0\n\\end{array}",
      "solution": "Solution. On completing squares we obtain\n\\[\n\\left(qzxwvtnp^{2}-50\\right)^{2}-\\left(hjgrksla^{2}-48\\right)^{2}=14^{2}\n\\]\n\nLetting \\( vndkrcema=qzxwvtnp^{2}, plxmoyghi=hjgrksla^{2} \\), we find\n\\[\n(vndkrcema-50)^{2}-(plxmoyghi-48)^{2}=14^{2}\n\\]\nand the graph of this equation in the \\( vndkrcema plxmoyghi \\)-plane is readily identified as a rectangular hyperbola with center at \\( (50,48) \\) and asymptotes\n\\[\n\\left\\{\\begin{array}{l}\nvndkrcema+plxmoyghi=98 \\\\\nvndkrcema-plxmoyghi=2 .\n\\end{array}\\right.\n\\]\n\nIn the present situation interest is confined to the first quadrant of the \\( vndkrcema plxmoyghi \\)-plane. For each point ( \\( vndkrcema, plxmoyghi \\) ) in the first quadrant there are four points of the required locus \\( tonmczahl \\), namely \\( ( \\pm \\sqrt{vndkrcema}, \\pm \\sqrt{plxmoyghi}) \\). Because the transformation \\( (qzxwvtnp, hjgrksla) \\mapsto(vndkrcema, plxmoyghi) \\) mapping each quadrant of the \\( qzxwvtnp hjgrksla \\)-plane onto the first quadrant of the \\( vndkrcema plxmoyghi \\)-plane is differentiable in both directions, the smooth arcs of the auxiliary graph correspond to smooth arcs of \\( tonmczahl \\).\nThe three points \\( (0,0),(0,96) \\), and \\( (100,0) \\) of the auxiliary graph lying on the boundary of the first quadrant correspond to five points ( 0,0 ), ( \\( 0, \\pm \\sqrt{96} \\) ), \\( ( \\pm 10,0) \\) of \\( tonmczahl \\) which require special consideration.\nThe function\n\\[\nskdptwre(qzxwvtnp, hjgrksla)=hjgrksla^{4}-qzxwvtnp^{4}-96 hjgrksla^{2}+100 qzxwvtnp^{2}\n\\]\nhas gradient\n\\[\nugfjdksa skdptwre=\\left(-4 qzxwvtnp^{3}+200 qzxwvtnp, 4 hjgrksla^{3}-192 hjgrksla\\right) .\n\\]\n\nSince \\( ugfjdksa skdptwre \\) does not vanish at the points \\( (0, \\pm \\sqrt{96}),( \\pm 10,0) \\), the curve \\( tonmczahl \\) is smooth at those points. The first component of \\( ugfjdksa skdptwre \\) vanishes at \\( (0, \\pm \\sqrt{96}) \\), so \\( tonmczahl \\) has horizontal tangents at these two points. The second component of \\( ugfjdksa skdptwre \\) vanishes at \\( ( \\pm 10,0) \\), so \\( tonmczahl \\) has vertical tangents at these points. At the origin, both components of \\( ugfjdksa skdptwre \\) vanish, so we consider the quadratic terms\n\\[\n100 qzxwvtnp^{2}-96 hjgrksla^{2}\n\\]\nof \\( skdptwre \\) at this point. Since these constitute a non-degenerate quadratic form which vanishes along the lines \\( hjgrksla= \\pm(100 / 96) qzxwvtnp \\), the curve \\( tonmczahl \\) crosses itself at the origin, the two branches being tangent to these two lines.\n\nExamination shows that the first component of \\( ugfjdksa skdptwre \\) does not vanish at any other points of \\( tonmczahl \\), so \\( tonmczahl \\) has no more horizontal tangents, but the second component of \\( ugfjdksa skdptwre \\) vanishes at eight more points of \\( tonmczahl \\), namely \\( ( \\pm 6, \\pm \\sqrt{48}),( \\pm 8, \\pm \\sqrt{48}) \\), so \\( tonmczahl \\) has vertical tangents at these points, corresponding to the vertical tangents on the auxiliary graph.\n\nSince the line \\( vndkrcema-plxmoyghi=2 \\) is an asymptote to the auxiliary hyperbola, \\( vndkrcema-plxmoyghi \\rightarrow 2 \\) along the unbounded arc of this hyperbola in the first quadrant. Correspondingly,\n\\[\nqzxwvtnp-hjgrksla=\\sqrt{vndkrcema}-\\sqrt{plxmoyghi}=\\frac{vndkrcema-plxmoyghi}{\\sqrt{vndkrcema}+\\sqrt{plxmoyghi}} \\rightarrow 0\n\\]\nalong the unbounded arc of \\( tonmczahl \\) in the first quadrant. Hence \\( tonmczahl \\) is asymptotic to the line \\( hjgrksla=qzxwvtnp \\) in the first quadrant. By symmetry \\( tonmczahl \\) is asymptotic to the same line in the third quadrant and to \\( hjgrksla=-qzxwvtnp \\) in the second and fourth quadrants.\nSince there are no points of the auxiliary locus in the strip \\( 36<vndkrcema<64 \\), there are no points of \\( tonmczahl \\) in the strips \\( 6<qzxwvtnp<8 \\) and \\( -8<qzxwvtnp<-6 \\).\n\nThe graph of \\( skdptwre(qzxwvtnp, hjgrksla)=0 \\) is therefore as shown.\nFor general methods of graphing higher-degree plane curves, see C. A. Stewart, Advanced Calculus, 3rd ed., Methuen, London, 1951, or J. H."
    },
    "kernel_variant": {
      "question": "Trace completely the real plane curve\n\\[\n\\boxed{\\;y^{4}-x^{4}-72y^{2}+120x^{2}=0\\;}.\\]\nIn particular, locate every singular point, determine all tangent directions there, find all points with horizontal or vertical tangents, describe the unbounded branches and their asymptotes, and indicate every open strip in the \\(x\\)-axis direction that contains no points of the curve. (A carefully reasoned description is sufficient; an actual drawing is *not* required.)",
      "solution": "Let \n f(x,y)=y^{4}-x^{4}-72y^{2}+120x^{2}.\n\nSTEP 1.  Complete squares.\nBecause\n  (x^{2}-60)^{2}=x^{4}-120x^{2}+3600,    (y^{2}-36)^{2}=y^{4}-72y^{2}+1296,\nwe get\n  y^{4}-72y^{2}=(y^{2}-36)^{2}-36^{2},    x^{4}-120x^{2}=(x^{2}-60)^{2}-60^{2}.\nHence\n  0=f(x,y)=[(y^{2}-36)^{2}-36^{2}]-[(x^{2}-60)^{2}-60^{2}]\n           =(y^{2}-36)^{2}-(x^{2}-60)^{2}+(60^{2}-36^{2}),\nand since 60^{2}-36^{2}=2304=48^{2},\n  (x^{2}-60)^{2}-(y^{2}-36)^{2}=48^{2}.\n\nSTEP 2.  Quadratic substitution.\nSet X=x^{2}≥0, Y=y^{2}≥0.  The curve becomes\n  (X-60)^{2} - (Y-36)^{2} = 48^{2},\nwhich is a rectangular hyperbola in the X Y–plane with center (60,36), transverse axis parallel to the X–axis, and asymptotes\n  X - Y = 24,    X + Y = 96.\n\nSTEP 3.  Domain restrictions in the first quadrant.\nFrom (X-60)^{2} ≥ 48^{2} we get |X-60| ≥ 48 ⇒ X ≤ 12 or X ≥ 108.  Thus in the first quadrant the hyperbola appears as two disjoint arcs: a bounded \"left\" arc for 0 ≤ X ≤ 12 and an unbounded \"right\" arc for X ≥ 108.\n\nSTEP 4.  Pulling back to the (x,y)–plane.\nEach point (X,Y) with X,Y≥0 lifts to four points (±√X, ±√Y) off the axes, and the correspondence is locally invertible there, carrying smooth arcs to smooth arcs.\n\nSpecial intersections with the axes:\n – x=0 ⇒ y^{4}-72y^{2}=0 ⇒ y=0 or y=±6√2.\n – y=0 ⇒ -x^{4}+120x^{2}=0 ⇒ x=0 or x=±2√30.\n\nSTEP 5.  Tangents and singularity via ∇f:\n ∇f =(-4x^{3}+240x,\n       4y^{3}-144y)\n      =(-4x(x^{2}-60), 4y(y^{2}-36)).\n(a) At (0,±6√2):  ∂f/∂x=0, ∂f/∂y≠0 ⇒ horizontal tangents.\n(b) At (±2√30,0): ∂f/∂y=0, ∂f/∂x≠0 ⇒ vertical tangents.\n(c) At (0,0):  ∇f=(0,0).  The quadratic part is\n    120x^{2}-72y^{2} = 24(5x^{2}-3y^{2}),\nwhich factors as (√5 x ± √3 y).  Hence the curve crosses itself at the origin with tangent lines\n    y = ±√(5/3) x.\n\nVertical tangents off the axes: ∂f/∂y=0 ⇒ y=0 or y=±6.  Excluding y=0, set y=±6 in f=0:\n  -x^{4}+120x^{2}-1296=0 ⇒ x^{2}=12 or 108.\nThus eight more points with vertical tangents:\n  (±2√3, ±6),  (±6√3, ±6).\nNo other horizontal tangents occur, since ∂f/∂x=0 only at x=0 or x=±√60, and x=±√60 yields no real solutions of f=0.\n\nAsymptotic behaviour:\nOn the unbounded branch in QI we have X-Y→24, X+Y→∞, so\n  x-y = (√X-√Y) = (X-Y)/(√X+√Y) → 0,\n  x+y → ∞.\nThus that branch is asymptotic to y=x.  By symmetry the branches in QIII also approach y=x, and those in QII and QIV approach y=-x.\n\nForbidden strips:\nSince the hyperbola has no points with 12 < X < 108, the original curve has no points with\n  2√3 < |x| < 6√3.\n\nFinal description.\nThe curve y^{4}-x^{4}-72y^{2}+120x^{2}=0\n • is symmetric about both axes and the origin;\n • crosses itself at (0,0) with tangent lines y=±√(5/3)x;\n • meets the axes at (0,±6√2) (horizontal tangents) and at (±2√30,0) (vertical tangents);\n • has eight additional vertical tangents at (±2√3,±6) and (±6√3,±6);\n • has no points in the strips 2√3 < |x| < 6√3;\n • has four unbounded branches—those in QI and QIII asymptotic to y=x, and those in QII and QIV asymptotic to y=-x.\nThis completes the tracing of the curve.",
      "_meta": {
        "core_steps": [
          "Complete squares to express the quartic as (x²−B)² − (y²−A)² = C²",
          "Substitute X = x², Y = y² to turn it into a second-degree curve (rectangular hyperbola) in the XY-plane",
          "Locate hyperbola’s center and asymptotes, then restrict to first quadrant",
          "Pull the picture back via (x,y) ↔ (√X,√Y); use ∇f to check smoothness, tangents, and the self–intersection at the origin",
          "Transfer asymptotic behavior and forbidden strips from the hyperbola to sketch the original curve"
        ],
        "mutable_slots": {
          "slot1": {
            "description": "coefficient of y² in the original equation (−A y² term)",
            "original": "96"
          },
          "slot2": {
            "description": "coefficient of x² in the original equation (+B x² term)",
            "original": "100"
          },
          "slot3": {
            "description": "translation constants after completing squares: (B/2 , A/2) i.e. hyperbola center",
            "original": "(50 , 48)"
          },
          "slot4": {
            "description": "constant on the right–hand side after completing squares, (B²−A²)/4 = C²",
            "original": "14²"
          },
          "slot5": {
            "description": "equations of the hyperbola’s asymptotes in XY-plane: X+Y = A/2 + B/2 and X−Y = B/2 − A/2",
            "original": "X+Y = 98 ,  X−Y = 2"
          }
        }
      }
    }
  },
  "checked": true,
  "problem_type": "calculation"
}