CM: test 4 (Vertical <,Triangle Sum Theorem)

The Triangle Sum Theorem states that the sum of the interior angles of a triangle is always 180 degrees.

The third angle measures 45 degrees, since 90 + 45 + x = 180.

To find an unknown angle, subtract the sum of the known angles from 180 degrees.

Vertical angles are equal; when two lines intersect, the opposite angles formed are congruent.

The sum of two supplementary angles is 180 degrees.

Angle 1 measures 19 degrees, since 180 - 161 = 19.

The measure of an exterior angle is equal to the sum of the measures of the two non-adjacent interior angles.

The third angle measures 90 degrees, since 30 + 60 + x = 180.

Complementary angles are two angles whose measures add up to 90 degrees.

The complement measures 45 degrees, since 90 - 45 = 45.