Half Angle Calculator
Calculate sine, cosine or tangent of θ/2 from an angle θ in degrees.
Formula
sin²(θ/2)=(1−cosθ)/2; cos²(θ/2)=(1+cosθ)/2; tan(θ/2)=sin(θ/2)/cos(θ/2).
Value at θ/2 ≈ sin((0.5×(60)-360×floor((0.5×(60)+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(60°/2)=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 θ/2 = 90° + 180°k, so the input θ = 180° + 360°k, for any integer k. Sine and cosine remain defined.
Sources
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