Give the reason
If angle A and B are supplementary, then Angle A + Angle B = 180
What is definition of supplementary
If B lies between A and C, then AB + BC = AC
What is segment addition postulate
Sum of the measures of the interior angles in a regular decagon
What is 1440
If two sides of a triangle are congruent, then the angles opposite them are also congruent
What is isosceles triangle theorem
If Ray AD bisects Angle ABC, then Angle ABD is 1/2 Angle ABC
What is angle bisector theorem