Circle Geometry Diagram: 36° Central Angles and Diameter Measurement #266853 (License: Personal Use)

This black-and-white diagram depicts a circle centered at point O, with diameter FA measuring 1.5 inches. The upper semicircle is subdivided by radii OB, OC, OD, and OE into five congruent central angles, each marked as 36°, confirming the full 180° arc. Points A through F lie on the circumference, forming a regular decagon’s top half when extended symmetrically.

Used in mathematics education (especially Euclidean geometry and trigonometry) to teach angle division, circle theorems, and polygon construction; commonly appears in textbooks, worksheets, or online learning modules explaining regular polygons or golden ratio relationships (e.g., pentagon/decagon constructions).