



Produced by Juliet Sutherland, David Wilson and the Online
Distributed Proofreading Team at http://www.pgdp.net









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  | Transcriber’s Note                                                 |
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  | In the original book the author used lowercase italic letters and  |
  | lowercase small capitals to label the geometric diagrams. These    |
  | have been here transcribed as lowercase and uppercase italic       |
  | letters respectively (_aA_).                                       |
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  | This file should be read using a font that supports the following  |
  | Unicode characters:                                                |
  |   ∠ angle, ∶ ratio, ∷ proportion, ∴ therefore, ′ prime, and        |