### Home > GC > Chapter 11 > Lesson 11.2.3 > Problem11-97

11-97.

88° = 2a

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.

$\frac{88 + 56}{2} = 72^\circ$