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Books Books 81 - 90 of 190 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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Plane and Solid Geometry

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...
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Entrance Examinations in Mathematics, 1884 to 1898 [with Supplements to 1900]

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....
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The Elements of Plane Geometry

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...
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Plane and Solid Geometry

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...
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Key to Milne's Plane and solid geometry

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) ...
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Plane and solid geometry

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...
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Plane Geometry

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....
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Elementary Geometry, Plane and Solid: For Use in High Schools and Academies

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...
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A Textbook on Sheet-metal Pattern Drafting, Volume 1

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 =...
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International Education Series

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...
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