Double Angle Calculator
Calculate sine, cosine or tangent of 2θ from an angle θ in degrees.
Formula
sin(2θ)=2sinθcosθ; cos(2θ)=cos²θ−sin²θ; tan(2θ)=sin(2θ)/cos(2θ).
Value at 2θ ≈ sin((2×(30)-360×floor((2×(30)+180)÷360))×pi÷180)
How to use
- Enter θ in degrees.
- Choose sine, cosine or tangent.
- Read the selected function at the transformed angle.
Examples
- sin(2×15°)=sin30°=1/2.
Frequently asked questions
Is the input in radians?
No. Enter degrees.
Are negative angles supported?
Yes. The sign follows the quadrant of the transformed angle.
Why can tangent fail?
Tangent is undefined when 2θ = 90° + 180°k, so the input θ = 45° + 90°k, for any integer k. Sine and cosine remain defined.
Sources
Updated: