| Wonders - 1877
...Earth, the Sun, and the star; when the Earth is at T', we measure the angle S T' E. In every triangle **the sum of the three angles is equal to two right angles,** — that is to say, to 180° ; then, if we make the sum of the two observed angles, STE and S T' E,... | |
| Wm. H. H. Phillips - Geometry - 1878 - 209 pages
...For the same reason, AB -\- BO AC : hence AB > AC— BC (Ax. 5). AB xvn. Theorem. In any triangle, **the sum of the three angles is equal to two right angles.** HYPOTH. Let ABC be any triangle. To BE PROVED. ZA -f- B + ACB = 2R. PROOF. Through the vertex of either... | |
| Charles Scott Venable - Geometry - 1881 - 366 pages
...that the angle FEG is the supplement of the angle BAC. PROPOSITION XXIX. THEOREM. In every triangle **the sum of the three angles is equal to two right angles.** Let ABC be any triangle. Produce the side CA towards D ; and at the point A draw AE, parallel to BC.... | |
| Adrien Marie Legendre - Geometry - 1882 - 181 pages
...The sum of two angles of a triangle is $ of a right angle ; what is the other angle equal to ? Since **the sum of the three angles is equal to two right angles** (P. XXV), the other angle must be equal to f of a right angle. 5. — One of the acute angles of a... | |
| WILLIAM T HARRIS - 1884
...If expressed, however, it would be something like this : " We have now shown that in this triangle **the sum of the three angles is equal to two right angles** ; but that is nothing peculiar or characteristic of the triangle before us, and it is therefore true... | |
| Philosophy - 1884
...It' expressed, however, it would be something like this : " We have now shown that in this triangle **the sum of the three angles is equal to two right angles** ; but that is nothing peculiar or characteristic of the triangle before us, and it is therefore true... | |
| Nathaniel Bowditch - Nautical astronomy - 1888 - 647 pages
...therefore the lines AB, CD, cannot meet, and must be parallel. IX. In any right-lined triangle, ABC, **the sum of the three angles is equal to two right angles.** To prove this, produce BC (in the fig. Theorem VII) toward D; then (by VII) the external angle ACD... | |
| Nikolaĭ Ivanovich Lobachevskiĭ - Geometry, Hyperbolic - 1891 - 50 pages
...Therefore |-(S— -) is the size of the quadrilateral ABCD and at the same time also that of the spherical **triangle in which the sum of the three angles is equal to** S. 28. If three planes cut each other in parallel lines, then the sum of the three surface angles equals... | |
| Thomas J. Foster - Coal mines and mining - 1891 - 415 pages
...side. 7. In an isosceles triangle the angles opposite the equal sides are equal. 8. In any triangle **the sum of the three angles is equal to two right angles,** or 180°. 9. If two angles of a triangle are given, the third may be found by subtracting their sum... | |
| International Correspondence Schools - History - 1900 - 637 pages
...side. 9. In an isosceles triangle, the angles opposite the equal sides are equal. 10. In any triangle, **the sum of the three angles is equal to two right angles,** or 180°. 11. If two angles of a triangle are given, the third may be found by subtracting their sum... | |
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