Double-Angle Formulas
Formulas expressing trigonometric functions of an angle 2x in terms of functions of an angle x,
sin(2x) = 2sinxcosx
(1)
cos(2x) = cos^2x-sin^2x
(2)
= 2cos^2x-1
(3)
= 1-2sin^2x
(4)
tan(2x) = [画像:(2tanx)/(1-tan^2x).]
(5)
The corresponding hyperbolic function double-angle formulas are
See also
Half-Angle Formulas, Hyperbolic Functions, Multiple-Angle Formulas, Prosthaphaeresis Formulas, Trigonometric Addition Formulas, Trigonometric Functions, Trigonometry Explore this topic in the MathWorld classroomExplore with Wolfram|Alpha
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Cite this as:
Weisstein, Eric W. "Double-Angle Formulas." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/Double-AngleFormulas.html