is an acute triangle with incircle . is tangent to sides , and at , and respectively. is a point on the altitude from such that , the circle with diameter , is tangent to . intersects and at and respectively. Given , and that the radius of is 5, compute .
Solution
By the Law of Sines we have . Let , and denote the center of , the point of tangency between and , and the center of respectively. Since we are told is acute, we can compute . Since and is tangent to , we find . Let be the foot of the altitude from to . Define to be the homothety about which sends to . We have , and conclude that , and are collinear. Now since is a diameter of is right, implying that is cyclic. Invoking Power of a Point twice, we have . Because we are given radius of we can find and . If we write in the usual manner with respect to triangle , we seek . But recall that Heron's formula gives us where is the area of triangle . Writing , we have . Knowing , we need only compute the ratio . By writing , we find . Now we compute our answer, .