1. Angles of Triangles
4.2

2. Angle Sum Theorem – The sum of the
measures of the angles of a triangle
is 180°.
Thm - If two angles of one triangle are ≅
to two angles of a second triangle, then
then the third angles are ≅

3. Exterior angle – formed by one side of a triangle
and the extension of another side. 1
Remote Interior angle – the interior angles of the
triangle that are NOT adjacent to the exterior
angle.

4. Exterior Angle Thm – The measure of an exterior <
of a triangle is equal to the SUM of the
remote interior angles.
Thm – The acute angles of a right triangle are
complementary.
Thm – There can be at most one right or one
obtuse angle in a triangle.