Maths Olympiad Prep

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Geometry Difficulty 4.6 AIME Find the answer

Consider an isosceles triangle TT with base 10 and height 12. Define a sequence ω1,ω2,\omega_{1}, \omega_{2}, \ldots of circles such that ω1\omega_{1} is the incircle of TT and ωi+1\omega_{i+1} is tangent to ωi\omega_{i} and both legs of the isosceles triangle for i>1i>1. Find the ratio of the radius of ωi+1\omega_{i+1} to the radius of ωi\omega_{i}.

A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.

Solution

The ratio of the radius of ωi+1\omega_{i+1} to the radius of ωi\omega_{i} is 49\frac{4}{9}.

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