Work out double angle formula instantly with clear inputs, formula shown and shareable results.
The double-angle formulas come from the sum formulas with both angles equal: sin 2θ = 2 sin θ cos θ, cos 2θ = cos²θ − sin²θ = 1 − 2sin²θ = 2cos²θ − 1, and tan 2θ = 2 tan θ / (1 − tan²θ).
Sine
sin 2θ = 2 sin θ cos θ
Cosine
cos 2θ = cos²θ − sin²θ = 1 − 2sin²θ
Tangent
tan 2θ = 2 tan θ / (1 − tan²θ)
sin 60° = 0.8660254, cos 60° = 0.5 and tan 60° = 1.7320508.
When 2θ is an odd multiple of 90°, for example θ = 45°. The calculator reports 0 there rather than infinity.