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