The measure of an inscribed angle is half the measure of the arc
that subtends it. This means that the measure of is
half the measure of arc . First, use this fact to solve for
the measure of arc .
If two secants of a circle intersect outside the circle, then the
measure of the angle that they form equals half the measure of the
minor intercepted arc subtracted from half the measure of the
major intercepted arc. Use this fact to find the measure of as follows:
Suppose and intersect at point . If two chords intersect at a
point inside a circle, then the measure of the included angle
equals half the sum of the measures of the two opposite arcs. Use
this fact to solve for the measure of .
Thus, the value of is 100.