# 4 Circles of Pi Day

Geometry Level 3

Two circles $$O_1 , O_2$$ are tangent to each other at point $$A$$ and has a common tangent $$L_1$$ at points $$B , C$$. Another line $$L_2$$ is parellel to line $$L_1$$ and tangent to circle $$O_1$$. If $$O_1$$ has a radius of 9, $$O_2$$ has a radius of 4, $$O_3$$ is tangent to $$O_1 , O_2$$ and $$L_1$$, $$O_4$$ is tangent to $$O_1 , O_2$$ and $$L_2$$, find the geometric mean of the radiuses of the 4 circles.

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