After remarking that the mathematician positively knows that the sum of the three angles of a triangle is equal to two right angles... Introduction and books 1,2 - Page 218by Euclid, Sir Thomas Little Heath, Johan Ludvig Heiberg - 1908Full view - About this book
| Edmund Whittaker - Science - 1949 - 212 pages
...could be replaced by the assertion that 'it is possible to divide space into equal cubes', or that 'the **sum of the three angles of a triangle is equal to two right** angles', or that 'a triangle exists similar to a given triangle but of arbitrary size '. Any one of... | |
| Education - 1896
...GEOMETRY.— i. What is Geometry? When are angles supplementary? When complementary? 2. Prove that the **sum of the three angles of a triangle is equal to two right** angles. 3. A straight line can not insersect the circumference of a circle in more than two places.... | |
| Physics
...the angle in a semicircle is less obvious. It is easy to prove it deductively if it is known that the **sum of the three angles of a triangle is equal to two right** angles, but otherwise not. And Thales is hardly likely to have known this; he did not think of an angle... | |
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