For the triangle shown above, where A, B and C are all points on a circle, and line segment AB has length 18, what is the area of triangle ABC? (1) Angle ABC measures 30°. (2) The circumference of the circle is 18pi. http://www.manhattangmat.com/images/inscribedtriangle/inscribedtriangl...

sorry, the pi didn't copy correctly. statement two has been modified.

any explication why is C?