Geometry - Chapter 5 Theorems

Theorems

Triangle Sum Theorem

The sum of the measures of the interior angles of a triangle is 180°.

Exterior Angle Theorem

The measure of an exterior angle of a triangle is equal to the sum of the measures of the two nonadjacent interior angles.

Corollary to the Triangle Sum Theorem

The acute angles of a right triangle are complementary.

Third Angles Theorem

If two angles of one triangle are congruent to two angles of another triangle, then the third angles are also congruent.

Base Angles Theorem

If two sides of a triangle are congruent, then the angles opposite them are congruent.

Converse of the Base Angles Theorem

If two angles of a triangle are congruent, then the opposite sides are congruent.

Corollary to the Base Angles Theorem

If a triangle is equilateral, then it is equiangular.

Corollary to the Converse of the Base Angles Theorem

If a triangle is equiangular, then it is equilateral.