 | George Albert Wentworth - Geometry - 1899 - 496 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... | |
 | George Albert Wentworth - Geometry, Plane - 1899 - 278 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.... | |
 | Charles Austin Hobbs - Geometry, Plane - 1899 - 266 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... | |
 | Thomas Franklin Holgate - Geometry - 1901 - 462 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... | |
 | Metal-work - 1901 - 548 pages
...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 - 420 pages
...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... | |
 | Education - 1903 - 692 pages
...uniformly. Casey (El. of Euclid, 8th ed., p. 299) says : " The discovery of the proposition that ' the sum of the three angles of a triangle is equal to two right angles ' is attributed to Pythagoras. Until modern times no proof of it, independent of the theory... | |
 | Presbyterianism - 1891 - 656 pages
...tests of other rational processes. This is true in mathematics. Thus, when once it is proven that the sum of the three angles of a triangle is equal to two right angles, no rational process can be accepted as true which in premise or conclusion contravenes this... | |
 | Education - 1904 - 938 pages
...straight line joining their centers is the perpendicular bisector of their common chord. 6. Prove: The sum of the three angles of a triangle is equal to two right angles. 7. (a) Circumscribe a circle about a given triangle. (&) Inscribe a circle In a given triangle.... | |
 | George Albert Wentworth - Geometry - 1904 - 496 pages
...equal angles are called homologous sides. BOOK I. PLANE GEOMETRY. PROPOSITION XVIII. THEOREM. 129. Tlie sum of the three angles of a triangle is equal to two right angles. ACF Let A, B, and BCA be the angles of the triangle ABC. To prove that ZA + ZB + Z BCA = 2... | |
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After remarking that the mathematician positively knows that the sum of the three angles of a triangle is equal to two right angles... 
