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
| Astronomy - 1844 - 352 pages
...some property is asserted, and the truth of it required to be proved : thus when it is said that the **sum of the three angles of a triangle is equal to two right** angles, that is a theorem, the truth of which is demonstrated by geometry. A set, or collection, of... | |
| Blaise Pascal - Apologetics - 1846 - 384 pages
...gradually arrived at the proof of the thirty-second proposition of the first book of Euclid : That the **sum of the three angles of a triangle is equal to two right** angles. Just at this moment, his father entered the apartment ; but so absorbed in thought was this... | |
| Jeremiah Day - Algebra - 1847
...equations, though they may not be presented to us under the algebraic forms. Thus the proposition, that the **sum of the three angles of a triangle is equal to two right** angles, (Euc. 32. 1.) may be demonstrated, either in common language, or by means of the signs used... | |
| Algebra - 1848
...equations, though they may not be presented to us under the algebraic forms. Thus the proposition, that the **sum of the three angles of a triangle is equal to two right** angles, (Euc. 32. 1,) may be demonstrated, either in common language, or by means of the signs used... | |
| CHARLES DAVIS, L.L. D. - 1850
...second, by Prob. VIII ; then will the angle HEF be equal to the third angle of the triangle. For, the **sum of the three angles of a triangle is equal to two right** angles (Bk. L Th. xvii) ; and the sum of the three angles on the same side of the line DE is equal... | |
| Charles Davies - Geometry - 1850 - 216 pages
...second, by Prob. VIII ; then will the angle HEF be equal to the third angle of the triangle. For, the **sum of the three angles of a triangle is equal to two right** angles (Bk. I. Th. xvii) ; and the sum of the three angles on the same side of the line DE is equal... | |
| Charles William Hackley - Trigonometry - 1851 - 372 pages
...and the other equal to 105° 30', it will be easy to find the third angle, by recollecting that the **sum of the three angles of a triangle is equal to two right** angles (Geom. Theorem 15), or 180° ; therefore subtracting the sum of the two given, 47° + 105°... | |
| Samuel Griswold Goodrich - Science - 1852 - 352 pages
...some property is asserted, and the truth of it required to be proved : thus when it is said that the **sum of the three angles of a triangle is equal to two right** angles, that is a theorem, the truth of which is demonstrated hy geometry. A set, or collection, of... | |
| Peter Nicholson - 1856
...; but the sum of the two angles BAC, BAD, is equal to two right angles (theorem 1) ; therefore the **sum of the three angles of a triangle is equal to two right** angles. 80. COROLLARY 1. — If two angles of one triangle be equal to two angles of another triangle,... | |
| Science - 1857
...first book of the ' Elements.' The proposition required by Euclid is the thirty-second, viz. that the **sum of the three angles of a triangle is equal to two right** angles ; given that proposition, the difficulty about parallels disappears, inasmuch as their properties... | |
| |