The figure below shows the circles O1 (radius r1) and O2 (radius r2). A1A2 and B1B2 are the common external tangents and CD is a common internal tangent. Circle O3 (radius r3) touches A1C, CD, and circle O1. Circle O4 (radius r4) touches B1D, CD, and circle O1. Prove that .
Geometric art is a form of art based on the use and application of geometric figures. A geometric figure is any set or combination of points, lines, surfaces and solids.
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Original problem 1099.