| William James Milne - Geometry - 1899 - 398 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 - 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.... | |
| 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° =... | |
| 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... | |
| 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... | |
| 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.... | |
| 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... | |
| 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... | |
| Isaac Newton Failor - Geometry - 1906 - 440 pages
...Isosceles. 1 f Acute. -{ I Oblique. Scalene. f Isosceles. v. Obtuse. 82 PROPOSITION XI. THEOREM 153 The **sum of the three angles of a triangle is equal to two right** angles.* HYPOTHESIS. ABC is any triangle. CONCLUSION. ZA + ZB + ZC = 2rt. A. PROOF Draw MN through... | |
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