Answer:
125 deg
Step-by-step explanation:
Keep these three rules in mind:
1) A central angle (vertex is the center of the circle) has the same measure as the arc it intercepts.
2) The measure of an inscribed angle (vertex is point on circle) is half the measure of the intercepted arc.
3) Opposite angles of a rectangle inscribed in a circle are supplementary.
110 deg is a central angle.
By rule 1), the arc intercepted by the central angle 110 deg also measures 110 deg.
a is an inscribed angle that intercepts an arc of 110 deg.
By rule 2), the measure of an inscribed angle is half the measure of the intercepted arc.
angle a measures 55 deg.
Rule 3) Angles a and b are supplementary.
a + b = 180
55 + b = 180
b = 125
