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Printsmc
geometry senior
Problem
Circles , , and each have radius and are placed in the plane so that each circle is externally tangent to the other two. Points , , and lie on , , and respectively such that and line is tangent to for each , where . See the figure below. The area of can be written in the form for positive integers and . What is ? 
(A)
(B)
(C)
(D)
Solution
Let and be the centers of and respectively and draw , , and . Note that and are both right. Furthermore, since is equilateral, and . Mark as the base of the altitude from to Since is a 30-60-90 triangle, and . Also, since and , we can find . Thus, . This makes So, our answer is . Note by diyarv: A way to see that is through similar triangles. Call the intersection between and . Since angles and are both right angles, and and are congruent, triangles and are similar by AA similarity. And, since is and is 2, the common ratio is . Using the fact that , we see that these lengths are and respectively. Using the Pythagorean theorem, we see that and are and respectively, giving us a sum of .
Final answer
D