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Books Books 91 - 100 of 187 on After remarking that the mathematician positively knows that the sum of the three....  
" 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 218
by Euclid, Sir Thomas Little Heath, Johan Ludvig Heiberg - 1908
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The School World: A Monthly Magazine of Educational Work and Progress, Volume 5

Education - 1903
...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...
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The Presbyterian Quarterly: 1891, Volume 5

Presbyterianism - 1891
...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...
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Biennial Report of the Superintendent of Public Instruction ..., Volumes 17-19

Washington (State). Superintendent of Public Instruction - Education - 1904
...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....
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Plane and Solid Geometry

George Albert Wentworth - Geometry - 1904 - 473 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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PLANE AND SOLID GEOMETRY

ISAAC NEWTON FAILOR - 1906
...Scalene. f Isosceles. fc Oblique. Acute. Scalene. f Isosceles. . Obtuse. PROPOSITION XL THEOREM 153 The sum of the three angles of a triangle is equal to two right angles.* HYPOTHESIS. ABC is any triangle. CONCLUSION. PROOF Draw MN through B II to AC, and produce...
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Plane and Solid Geometry

Isaac Newton Failor - Geometry - 1906 - 418 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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Exercises in Concrete Geometry: With Supplementary Discussions

David Sands Wright - Geometry - 1906 - 84 pages
...the bisectors of a pair of supplementary adjacent angles meet at an angle of 90. 5. Theorem. The sum of the three angles of a triangle is equal to two right angles. 1. How many degrees in each angle of the triangle ABC, if they are in the proportion of 1,...
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A Study of Mathematical Education: Including the Teaching of Arithmetic

Benchara Branford, George Parker Bidder - Mathematics - 1908 - 392 pages
...body of scientific theorems. Allman attributes to Thales the discovery of the two theorems (a) The sum of the three angles of a triangle is equal to two right angles ; (&) The sides of equi-angular triangles are proportional. (Hence the basis of the theory of...
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The Journal of Philosophy, Psychology and Scientific Methods

Philosophy - 1909
...eloquently, and we can not stifle her voice. But our intellect also tells us, and with equal force, that the sum of the three angles of a triangle is equal to two right angles, and we are unable to rebel against its authority. If we see God behind the categorical imperative,...
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Wentworth's Plane Geometry

George Albert Wentworth, David Eugene Smith - Geometry, Plane - 1910 - 287 pages
...side of the transversal are supplementary, the lines are parallel. PROPOSITION XIX. THEOREM 107. The sum of the three angles of a triangle is equal to two right angles. c Given the triangle ABC. Y To prove that Z .4 + Z 7?+ Z (7 = 2 rt. A. Proof. Suppose BY drawn...
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