benpack03 wrote:

If you say that the base forms a right angle with the center of the circle, you can use pythagoreans theorm and get x^2 + x^2 = 12^2 - and from this you can get r=6 root of 2. Using c=2 pi r you can assume that the triangle takes up i/4 of the circle and multiply the circumference times 3/4 you get 9 pi root of 2 as the answer. This is assuming a lot from this problem, it needs to tell more.

The problem statement must be little more informative.