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    Double-angle Formulas

    Alternate names

    double-angle identities | trigonometric double-angle identities

    Basic definition

    The double-angle formulas are a set of formulas that express trigonometric functions of twice an angle in terms of the trigonometric functions of the original angle.

    Detailed definition

    Formulas expressing trigonometric functions of an angle 2x in terms of functions of an angle x, sin(2x) | = | 2sin x cos x cos(2x) | = | cos^2 x - sin^2 x | = | 2cos^2 x - 1 | = | 1 - 2sin^2 x tan(2x) | = | (2tan x)/(1 - tan^2 x).

    Related terms

    half-angle formulas | hyperbolic functions | multiple-angle formulas | prosthaphaeresis formulas | trigonometric addition formulas | trigonometric functions | trigonometry

    Educational grade level

    high school level (California trigonometry standard)

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