Art of problem 1439, Generative Sketching.
In the figure below, the circles A,B,C,D are tangent to the circle O; a, b, c, d, x, y are the length of the exterior common tangent to circles A and B, B and C, C and D, D and A, A and C, and B and D respectively. Prove the generalized Ptolemy's theorem: \(x \cdot y = a \cdot c + b\cdot d\).
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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