Short, but yet plain elements of geometry shewing how by a brief and easie method, most of what is necessary and useful in Euclid, Archimedes, Appollonius, and other excellent geometricians, both ancient and modern, may be understood / written in French by F. Ignat. Gaston Pardies. And render'd into English, by John Harris.
- Ignace-Gaston Pardies
- Date:
- 1734
Licence: Public Domain Mark
Credit: Short, but yet plain elements of geometry shewing how by a brief and easie method, most of what is necessary and useful in Euclid, Archimedes, Appollonius, and other excellent geometricians, both ancient and modern, may be understood / written in French by F. Ignat. Gaston Pardies. And render'd into English, by John Harris. Source: Wellcome Collection.
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![the fame Side equal to twe Right ones ; that is, & — ‘added to abe are equal to two Right Angles(by 1. 32.) But the Anglea de contains the two Angles à and 4. So that © the Angle 4 added tod added to 4, will be equal to two Right ones: But ¢ being equal to 4, it will fol- : .… low, that a added to £ added toc. or the Sum of all three together, . muft be equal to two Right ones: Which was to be proved. | 10. If any Side of a Triangle be produced, or mises drawn out, the external Angle a - will be equal to the two in- ternal oppofite Angles (taken pages together.) Let the Triangle be a elb : abc, whole Bafecd draw out DT 7€ to 4, by which means a new Angle, as e, will be made, which is called the Exrerzal Angle of that Trian- gle. Then I fay, That that external Angle, is e- qual] to both the internal and oppofite ones 4 and c. For thofe Angles 4 and c, together with J, are e- qual to two Right ones (by the-Precedent) and fo alfo are e and J, by (r.20.) wherefore e muft be e- qual to 4 added toc, becaufe together with b it makes two Right Angles, as they do. Q. E.D.. ~ COROLLARIES. f. The Sum of the three Angles of all Triangles | isthe fame. °° ta. No Triangle can have above one Right, or Dbtatetngte, ‘srt gaia 39 4d, Anat Sean 3. If 2](https://iiif.wellcomecollection.org/image/b33021995_0030.jp2/full/800%2C/0/default.jpg)


