Question

The measure of ADC is 200 degrees, and lines AB and BC are tangent to this circle. What is the measure of angle ECA?

Answer 1

m∠ECA = 10°

Explanation:

measure of arc AC is 360 - 200 = 160

arc AC is bisected by BE so the measure of the intercepted arc of angle BEC is 80. Then m∠BEC = 80 since it is a central angle. The angles formed by BE intersecting AC are right angles. So, m∠ECA = 90 - 80 = 10

It would have been a lot easier to explain this if they had labeled the point of intersection of BE and AC