### Home > GC > Chapter 6 > Lesson 6.2.5 > Problem 6-85

6-85.

For each shape below, use the geometric relationships to solve for the given variable(s). Show all work. Name the geometric relationships you used.

What is the sum of the angles within a triangle?

, Triangle Angle Sum

What do the tick marks on the sides of the triangles mean?

, Isosceles triangle

Extend the parallel sides.

Parallel lines have same side interior supplementary angles.

By the Equal Values Method:

Parallel lines

Use the Law of Cosines to solve for the unknown side.