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The Double-Angle Formulas

by Roger B. Nelsen (Lewis and Clark College)

This article originally appeared in:
College Mathematics Journal
January, 1989

Subject classification(s): Geometry and Topology | Analytic Geometry | Circles | Trigonometry | Trigonometric Identities
Applicable Course(s): 2.2 Trigonometry | 3.0 Calculus

A standard picture proof of the double angle formula for sine and cosine

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Capsule Course Topic(s):
One-Variable Calculus | Background
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