In the circle below, AB || CD, AD is a diameter of the circle, and AD = 36".What is the length of AB in inches? Express your answer in terms of pi. I got 18 * sin(80)/sin(50) but I do not know how to express it using pi.

Your answer 18 * sin(80)/sin(50) works out to 20 + pi.

Sorry, but it does not. I was able to convert it to 36 * sin(2pi/9).