Tangent to Perpendicular Radius Circle Theorem Small 320×231 Medium 640×462 Large 1024×740 Download TIFF Original 2400×1734 | (212.3 KB) Description Illustration used to show that "A tangent to a circle is perpendicular to the radius drawn to the point of tangency." Keywords circle, geometry, perpendicular, point of tangency, proof, proofs, prove, radius, tangent, tangents, theorem, theorems Galleries Geometric Theorems and Proofs Source: C.A. Hart, Daniel D. Feldman Plane and Solid Geometry (New York, NY: American Book Company, 1911)