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MATH 01310 · College Geometry

MATH 01310 · Circles & advanced Euclidean themes

Circle theorems (inscribed/central angles)

Definition

A central angle equals its intercepted arc’s measure. An inscribed angle is half the intercepted arc. Angle in a semicircle is a right angle. Parallel chord / tangent-chord theorems expand the toolkit.

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Inscribed angles subtending the same arc are congruent.

Tangent ⊥ radius at point of contact. Two tangents from an external point are congruent.

Intersecting chords, secants, and tangent-secant have power-of-a-point length relations.

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  1. 1.If arc AB is 80°, find the inscribed angle subtending arc AB.