Double Angle Identities
More Lessons for PreCalculus
Math Worksheets
Videos, worksheets, games and activities to help PreCalculus students learn about the double angle identities.
What are the Double-Angle Identities or Double-Angle Formulas?
sin(2x) = 2sin(x)cos(x)
cos(2x) = cos2(x) - sin2(x) = 1 - 2sin2(x) = 2cos2(x) - 1
How to use the Double-Angle Identities or Double-Angle Formulas?
Double-Angle Formulas
A few examples that use double-angle formulas from trigonometry.
Double Angle Formulas :
The double angles sin(2x) and cos(2x) can be rewritten as sin(x + x) and cos(x + x).
Applying the cosine and sine addition formulas, we find that sin(2x) = 2sin(x)cos(x).
Also, cos(2x) = cos2(x) - sin2(x)
How to use the sine and cosine addition formulas to prove the double-angle formulas.
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