Chapter 6 - Review Exercises - Page 315: 12

Angle 1: 50 degrees Angle 2: 40 degrees Angle 3: 90 degrees Angle 4: 50 degrees

Angle 3 is 90 degrees, for an inscribed angle is half of the value of the angle of the corresponding arc (the corresponding arc has an angle of 180 degrees). Angle 1, therefore, equals $180-90-40=50$ degrees. Since angle 1 corresponds to arc CB, arc CB is twice the measure of angle 1, making it 100 degrees. Angle 4 is half the measure of arc CB, so it is 50 degrees. Thus, angle 2 is: $180-90-50=40$ degrees.