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
| James Howard Gore - Geometry - 1898 - 210 pages
...a triangle is greater than the difference of the other two sides. PROPOSITION XII. THEOREM. 79. The **sum of the three angles of a triangle is equal to two right** angles. Let ABC be any triangle. To prove that Z A + Z B + Z BC A is equal to two right angles. From... | |
| Yale University - History - 1898
...circular sheet of tin 16 inches in diameter and weighing 8.2 ounces per square foot. JUNE 1896. (a) 1. The **sum of the three angles of a triangle is equal to two right** angles. 2. Construct a circle having its center in a given line and passing through two given points.... | |
| Charles Austin Hobbs - Geometry, Plane - 1899 - 240 pages
...angles of an inscribed quadrilateral are supplementary. Ex. 283. Prove by the use of Prop. 124 that the **sum of the three angles of a triangle is equal to two right** angles. Proposition 125. Problem. 158. At a given point in a given straight line, to erect a perpendicular... | |
| George Albert Wentworth - Geometry - 1899 - 473 pages
...sides opposite the equal angles are called homologous sides. PROPOSITION XVIII. THEOREM. 129. Tlie **sum of the three angles of a triangle is equal to two right** angles. BE A c ~F Let A, B, and BCA be the angles of the triangle ABC. To prove that ZA + ZB + Z BCA... | |
| William James Milne - Geometry, Solid - 1899 - 313 pages
.... : the required ¿. = 180° - 76° = 104°. Ex. 59. Show by each of the following figures that the **sum of the three angles of a triangle is equal to two right** angles, assuming that the construction lines чrе drawn as they appear to be drawn. Proof. (1) §... | |
| William James Milne - Geometry - 1899 - 384 pages
...49°, and 74° ? PLANE GEOMETRY.— BOOK I. Ex. 59. Show by each of the following figures that the **sum of the three angles of a triangle is equal to two right** angles, assuming that the construction lines are drawn as they appear to be drawn. Proposition XXIII... | |
| George Albert Wentworth - Geometry, Plane - 1899 - 256 pages
...sides opposite the equal angles are called homologous sides. PROPOSITION XVIII. THEOREM. 129. Tfie **sum of the three angles of a triangle is equal to two right** angles. Let A, B, and BCA be the angles of the triangle ABC. To prove that ZA + ZB + Z BCA = 2 rt.... | |
| Thomas Franklin Holgate - Geometry - 1901 - 440 pages
...equals the sum of Zs CAB and CBA That is, Z.ACD equals the sum of Zs CAB and CBA. 101. COROLLARY I. The **sum of the three angles of a triangle is equal to two right** angles. 102. COROLLARY II. The two acute angles of any right triangle are complementary ; ie their... | |
| International Correspondence Schools - Patternmaking - 1901
...pentagon are 40.5, 30.6'>, 51.25, 32.75, and 36.85; find the perimeter. Ans. 192 ft. TRIANGLES. 47. The **sum of the three angles of a triangle is equal to two right** angles, <>r 180°. Thus, the sum of the three angles A, B, and C, Fig. 31, is 59° + 73° + 48° =... | |
| William T. Harris, A. M., LL. D. - 1902
...of mathematical demonstration. No experimental process can ever establish the general truth that the **sum of the three angles of a triangle is equal to two right** angles. We should not confound " geometrical recreations'" with geometrical science.—(P.) t Isoperimetric... | |
| |