Question

find the measure of the arc. mbc = ?°

Explanation:

Step1: Note circle - central angle relation

The measure of an arc is equal to the measure of its central - angle.

Step2: Find central angle of arc BC

Assume the central angle of arc BC is $\angle BOC$. Since the circle is divided into 4 equal - parts (as there are 4 right - angles at the center), and the sum of angles around a point is $360^{\circ}$, each part is $\frac{360^{\circ}}{4}=90^{\circ}$.

Answer:

$90$