### Home > GC > Chapter 11 > Lesson 11.2.3 > Problem 11-97

11-97.

88° = 2*a*

Use the Triangle Angle Sum Theorem to solve for *b*.

*c* = (2)(∠*b*)

Look above at the image of the circle.

72° + *d* = 180° because they are supplementary angles.

Since *c* is equal to 56°, the vertical angles (72°) are the average of the two arcs they intercept.