Key Concepts: Special Segments in a Circle

Chord-Chord Product

If two chords intersect inside a circle, then the products of their segments are equal:

AE × EB = CE × ED

Secant-Secant Product

If two secants are drawn from an external point, then:

(whole₁)(external₁) = (whole₂)(external₂)

Secant-Tangent Product

If a secant and a tangent are drawn from the same external point, then:

(tangent)² = (whole secant)(external part)