Recall that the measure of the intercepted arc of an inscribed angle is twice the measure of that inscribed angle. Also recall that the sum of all angles in a circle is 360°. So, in order to find a missing arc measure, subtract the known arc measures from 360°. Then, it is possible to find any inscribed angle, since all of their intercepted arcs are known. When inscribed angles intercept the same arc, their measures are congruent.