Let A, B, and C be three points on circle O such that AC is a diameter of O. Extend line AC
to a point D such that DB is tangent to O at B, and suppose that \ADB = 20o. Compute
\ACB.  Choose the most appropriate option:
A) 32o  B) 47o  C) 55o  D) 68o  E) 71o
Since we did not specify in which direction to extend the line AC, we also accepted   35 as an acceptable answer.   Let O be the center of the circle. Through angle chasing, we can determine that   \BOD = 90o - \ADB = 70o   \A55oB =   180o - \BOD/2= 55o   correct answer 55o
<result>C</result>
Let A, B, and C be three points on circle O such that AC is a diameter of O. Extend line AC
to a point D such that DB is tangent to O at B, and suppose that \ADB = 20o. Compute
\ACB.