Golden Ratio In A Pentagon
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.
Keywordscircle, ptolemy, inscribed, circumscribed, golden ratio, golden mean, golden proportion, golden section, extreme ratio, mean ratio, medial section, golden cut, divine section, regular pentagon, Ptolemy's theorem
Florida Center for Instructional Technology Clipart ETC (Tampa: University of South Florida, 2007)