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Printsmc
geometry senior
Problem
Triangle and point in the same plane are given. Point is equidistant from and , angle is twice angle , and intersects at point . If and , then 
(A)
(B)
(C)
(D)
Solution
The product of two lengths with a common point brings to mind the Power of a Point Theorem. Since , we can make a circle with radius that is centered on , and both and will be on that circle. Since , we can see that point will also lie on the circle, since the measure of arc is twice the measure of inscribed angle , which is true for all inscribed angles. Since is a line, we have , which gives , or . We now extend radius to diameter . Since is a line, we have , which gives , or . Finally, we apply the power of a point theorem to point . This states that . Since and , the desired product is , which is .
Final answer
A