Here's me trying to do the problem. http://s10.postimg.org/bwwliium1/image.jpg
So this problem was from a textbook and it was in the chapter of the theorem: If $\theta$ is the angle subtended by a chord $PB$ at a point on a circle of a radius $r$, then $\sin \theta = PB/2r$.
I think the answer is 2, but I got 1.
Also, I know I can do area of triangle divided by half of the perimeter which is 2 in this case, but I want to see how I can apply the theorem to solving this.
!!EDIT!! I figured out what was wrong. The question says "...circle may be drawn through the three vertices of any triangle..." I think it meant circumscribed. That makes sense. Sorry about the confusion. Thanks for all your answers.