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" In every triangle the sum of the three angles is equal to two right angles. "
Elements of Plane and Spherical Trigonometry: With Numerous Practical Problems - Page 259
by Horatio Nelson Robinson - 1880 - 208 pages
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Elements of Geometry

Adrien Marie Legendre - Geometry - 1819 - 574 pages
...Consequently the four united, or the three BAC, ABC, ACB, are together equal to two right angles ; therefore in every triangle the sum of the three angles is equal to two right angles. We see by this that the theorem, considered a priori, does not depend upon a series...
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Elements of Geometry and Trigonometry: With Notes

Adrien Marie Legendre - Geometry - 1822 - 394 pages
...In that case, DEH and BAC would be together equal to two right angles. PROPOSITION XXVII. THEOREM. In every triangle, the sum of the three angles is equal to two right angles. Let ABC be any triangle. Produce the side CA towards D ; and, at the point A, draw...
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Elements of Geometry...: Translated from the French for the Use of the ...

Adrien Marie Legendre, John Farrar - Geometry - 1825 - 280 pages
...equal. In this case the angle DEH and the angle BA C would together make two right angles. THEOREM. 72. In every triangle the sum of the three angles is equal to tm* right angles. Fig.41. Demonstration. Let ABC (fig. 41) be any triangle; produce the side CA toward...
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Elements of Geometry...: Translated from the French for the Use of the ...

Adrien Marie Legendre, John Farrar - Geometry - 1825 - 294 pages
...this case the angle 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...
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Elements of Geometry: With Notes

John Radford Young - Euclid's Elements - 1827 - 228 pages
...exterior angle ACD. 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...
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A New and Easy Introduction to the Mathematics: Containing. A system of ...

Ira Wanzer - Arithmetic - 1831 - 408 pages
...degrees, is cnll«ii an 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...
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Inductive Geometry, Or, An Analysis of the Relations of Form and Magnitude ...

Charles Bonnycastle - Geometry - 1834 - 670 pages
...Another property of 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...
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Elements of Geometry and Trigonometry

Adrien Marie Legendre - Geometry - 1836 - 394 pages
...but DEF is equal to BAC : hence, DEH + BAC is equal to two right angles. PROPOSITION XXV. THEOREM. In every triangle the sum of the three angles is equal to two right angles. Let ABC be any triangle : then will the an- R glc C + A + B be equal to two right...
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The First Six Books of the Elements of Euclid: With a Commentary and ...

Dionysius Lardner - Geometry - 1838 - 382 pages
...otherwise prolix and tedious. It is as follows, being the 18th proposition of Legendre's first book. In every triangle the sum of the three angles is equal to two right anglet. Let ABC be the proposed triangje in which we shall suppose that AB is the greatest...
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Pantology: Or, A Systematic Survey of Human Knowledge; Proposing a ...

Roswell Park - Best books - 1841 - 722 pages
...side is opposite to the greater angle : and either side is always less than the sum of the other two. In every triangle, the sum of the three angles is equal to two right angles, or 180°. When two triangles have the angles of the one equal to the corresponding...
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