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An exterior angle of a triangle is equal to the sum of the two opposite interior angles.
Junior High School Mathematics ... - Page 29
by Edson Homer Taylor, Fiske Allen - 1923

Plane and Solid Geometry

Isaac Newton Failor - Geometry - 1906 - 431 pages
...equal. 157 COROLLARY 4. Each angle of an equilateral triangle is 60°. PROPOSITION XII. THEOREM 158 An exterior angle of a triangle is equal to the sum of the opposite interior angles. HYPOTHESIS. ACD is an exterior angle of the triangle ABC. CONCLUSION....

Plane Geometry

Edward Rutledge Robbins - Geometry, Plane - 1906 - 268 pages
...the triangle, at the other vertices are the opposite interior angles. [ZA and Z ('.] 108. THEOREM. An exterior angle of a triangle is equal to the sum of the opposite interior angles. Given: A ABC; exterior Z ABD. To Prove : Z ABD = ZA + Z C. Proof : Suppose...

Plane and Solid Geometry

Isaac Newton Failor - Geometry - 1906 - 440 pages
...equal. 157 COROLLARY 4. Each angle of an equilateral triangle is 60°. PROPOSITION XII. THEOREM 158 An exterior angle of a triangle is equal to the sum of the opposite interior angles. HYPOTHESIS. ACD is an exterior angle of the triangle ABC. CONCLUSION....

Plane and Solid Geometry

Edward Rutledge Robbins - Geometry - 1907 - 428 pages
...the triangle, at the other vertices are the opposite c A interior angles. [ZA and Z cj 108. THEOREM. An exterior angle of a triangle is equal to the sum of the opposite interior angles. Given: A ABC; exterior Z ABD. To Prove : Z ABU = ZA + Z C. Proof: Suppose...

New Plane Geometry

Webster Wells - Geometry, Plane - 1908 - 208 pages
...4. Since IIs AB and CE are cut by BC, 85. We have, from § 84, ^BCD = ^a + Z b = ^A + Z B. ^ Hence, an exterior angle of a triangle is equal to the sum of the two opposite interior angles. '- The following are immediate consequences of §§ 84, 85 : rP~86. An exterior angle of a triangle...

New Plane and Solid Geometry

Webster Wells - Geometry - 1908 - 338 pages
...4. Since !!s AB and CE are cut by BC, 85. We have, from § 84, Z BCD = Z Hence, an exterior tingle of a triangle is equal to the sum of the two opposite interior angles. The following are immediate consequences of §§ 84, 85 : 86. An exterior angle of a triangle is greater...

Biennial Report of the State Superintendent of Public Education to the ...

Louisiana. Department of Education - Education - 1908 - 366 pages
...it. one straight line intersect another straight line, the opposite angles are equal. 5. Prove that an exterior angle of a triangle is equal to the sum of their opposite interior angles. 6. Prove that if a straight line is perpendicular to one of two parallels,...

Notes on Physics

Benjamin Warner Snow - Physics - 1909 - 810 pages
...the second surface, so that D = d+d'. But d = i — r. and d'=V— r', therefore But r + r' = A, (the exterior angle of a triangle is equal to the sum of the two opposite interior angles), where A is equal in magnitude to the angle of the prism (their sides being perpendicular). If now the...