## Abstract

**Triangle**. The sum of two sides of a triangle (Fig. 79) is always greater than the third side:

*b*+

*c*>

*a*. The sum of angles of a triangle: α + β + γ = 180°. A triangle is completely determined, when there are given: (1) three sides or (2) two sides and the angle included between them, or (3) one side and two angles adjacent to it. Two sides and an angle opposite to one of them determine either two triangles or one, or no triangle, in various cases (see Fig. 80, and, for details, pp. 221, 222).

## Keywords

Dihedral Angle Regular Polygon Plane Angle Central Angle Interior Angle
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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## Notes

- (1).
- (1).In these formulas, AB denotes the degree measure of the arc
*AB*equal to the degree measure of the central angle*AOB*.Google Scholar - (1).For determinants see p. 172.Google Scholar

## Copyright information

© Verlag Harri Deutsch, Zürich 1973