Formulas expressing trigonometric functions of an angle 
in terms of functions of an angle 
,
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(1) |
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(2) |
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(3) |
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(4) |
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(5) |
The corresponding hyperbolic function double-angle formulas are
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(6) |
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(7) |
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(8) |
See also
Half-Angle Formulas, Hyperbolic Functions, Multiple-Angle Formulas, Prosthaphaeresis Formulas, Trigonometric Addition Formulas, Trigonometric Functions, Trigonometry Explore this topic in the MathWorld classroom
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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