Golden Ratio In A Pentagon

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Illustration showing how the golden ratio in a regular pentagon (inscribed in a circle) can be found using Ptolemy’s theorem. The lines that are bolded form a quadrilateral. Ptolemy’s theorem says the square of b equals the sum of a squared and ab, which in turn gives the golden ratio.


Golden Mean


Florida Center for Instructional Technology Clipart ETC (Tampa: University of South Florida, 2007)


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