### Home > MC2 > Chapter 8 > Lesson 8.2.5 > Problem 8-80

8-80.

The three triangles are highlighted:

Triangle *ABD* has two sides of equal length.

Notice the size of the angles of the other two triangles.

Triangle *ABC*

Triangle *ABD*

Triangle *BCD*

Triangle *ABD* is an isosceles triangle, triangle *ABC* is acute, and triangle *BCD* is obtuse.

If two angles are supplementary, what is their sum?