2004 AIME II Problems/Problem 13
Let be a convex pentagon with and Given that the ratio between the area of triangle and the area of triangle is where and are relatively prime positive integers, find
Let the intersection of and be . Since it follows that is a parallelogram, and so . Also, as , it follows that .
By the Law of Cosines, . Thus the length similarity ratio between and is .
Let and be the lengths of the altitudes in to respectively. Then, the ratio of the areas .
However, , with all three heights oriented in the same direction. Since , it follows that , and from the similarity ratio, . Hence , and the ratio of the areas is . The answer is .
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