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Books Books 1 - 10 of 70 on In any triangle, the sum of the three angles is equal to two right angles, or 180..
" In any triangle, the sum of the three angles is equal to two right angles, or 180. "
Introduction and books 1,2 - Page 218
by Euclid, Sir Thomas Little Heath, Johan Ludvig Heiberg - 1908
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Elements of Plane and Spherical Trigonometry: With Their Applications to ...

Olinthus Gregory - Plane trigonometry - 1816 - 244 pages
...• — -', it will become gin c = sin A cos H + sin it cos A, Now, since in every plane triangle, the sum of the three angles is equal to two right angles, A + B = supplement of c ; and, since an angle and its supplement have the same sine, it follows that...
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Elements of Geometry

Adrien Marie Legendre - Geometry - 1819 - 208 pages
...case the angle DEH and the angle BAC would together make two right angles. THEOREM. In. every triangle the sum of the three angles is equal to two right angles. , 41. Demonstration. Let ABC (Jig. 41) be any triangle; produce the side CA toward D, and draw to the...
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American Practical Navigator

Nautical astronomy - 1821
...therefore the lines AB, CD cannot meet, and must be parallel. XXXV. In any right lined triangle ABC, the sum of the three angles is equal to two right angles. To prove this, you must produce BC (in ihefig. art. 33,) towards T), then (by'irt. 33) the external...
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Description and use of a diagram of navigation: by which all problems in ...

George Watson, George Watson (of Belfast, Maine.) - Transportation - 1822 - 64 pages
...sides. 196. The longest side bf any triangle is opposite the greatest angle. 195. In all plane triangles the sum of the three angles is equal to two right angles, or 180 deg. 198. An angle in a segment less than a semicircle is greater than a right angle. 197. An...
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Elements of Geometry and Trigonometry: With Notes

Adrien Marie Legendre - Geometry - 1822 - 367 pages
...Note II. of his Geometry, gives of the fundamental proposition, that, in every rectilineal triangle, the sum of the three angles is equal to two right angles. This demonstration is the more remarkable, as it makes no use of the theory of parallels, but, on the...
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Elements of Geometry...: Translated from the French for the Use of the ...

Adrien Marie Legendre, John Farrar - Geometry - 1825 - 224 pages
...DEH and the angle BAC would together make two right angles. 27 THEOREM. A. ' 72. In every triangle the sum of the three angles 'is equal to two right angles. Pig. 41. Demonstration. Let ABC (fig. 41) be any triangle ; produce the side CA toward D, and draw...
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Elements of geometry: with notes

John Radford Young - Geometry, Plane - 1827 - 208 pages
...Cor. 1. Since the angle ACD together with ACB make two right angles, it follows that in every triangle the sum of the three angles is equal to two right angles. Cor. 2. Hence if two angles in one triangle be equal to two in another, the third angle in the one...
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A new and easy introduction to the mathematics: containing. A system of ...

Ira Wanzer - Arithmetic - 1831 - 396 pages
...acute angle ; and one which is greater than 90 degrees, is said to |-" obtuse. — In every triangle, the sum of the three angles is equal to two right angles, or 180 degrees. Right angled triangles are in called because the angle included between lhe base and...
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A course of mathematics: for the use of academies, as well as private ...

Charles Hutton - Mathematics - 1831
...— — , it will become a sin. A = sin. n . cos. c+sin. c . cos. B. But, in every plane triangle, the sum of the three angles is equal to two right angles ; therefore, B and c are equal to the supplement of A : and, consequently, since an angle and its supplement...
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Inductive Geometry, Or, An Analysis of the Relations of Form and Magnitude ...

Charles Bonnycastle - Geometry - 1834 - 631 pages
...the latter will immediately follow from the principle already demonstrated, that in every triangle the sum of the three angles is equal to two right angles. For since the angle at C is a right angle, the sum of the remaining angles will be together equal to...
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