Angle BCD is a circumscribed angle of circle A. Angle BCA measures 40°. What is the measure of minor arc BD?

100°

Step-by-step explanation:

From the image attached, line BC and line CD are tangents to circle A. Also, AB and AD are the radius of the circle. The tangent theorem states that the angle between a tangent and the radius is 90°. Therefore:

∠ABC and ∠ADC = 90°.

Given triangle ABC:

∠ABC + ∠BCA + ∠CAB = 180°

∠CAB = 180 - ∠ABC - ∠BCA = 180 - 90 - 40 = 50

∠CAB = 50°

From the two tangent theorem, tangents that meet at the same point have the same length. This means BC = CD, ∠ACD = ∠BCA, ∠CAB = ∠CAD.

arc BD = ∠CAB + ∠CAD = 50 + 50

arc BD = 100°