Inscribed Angle in a Circle Proof Small 283×320 Medium 566×640 Large 906×1024 Download Tiff Original 2123×2400 | (273.1 KB) Description Illustration of a circle with an inscribed angle that can be used to prove that "An inscribed angle is measured by one half of its intercepted arc." In this case, center O lies outside angle ABC. Keywords angles, circle, circles, geometry, inscribed angle Galleries Geometric Theorems and Proofs Source: C.A. Hart, Daniel D. Feldman Plane and Solid Geometry (New York, NY: American Book Company, 1911) Courtesy the private collection of Roy Winkelman