Work out trigonometric identity checker instantly with clear inputs, formula shown and shareable results.
An identity holds for every admissible angle, so evaluating both sides numerically at a test angle is a quick sanity check. Agreement to within floating-point tolerance confirms the identity at that angle; genuine identities agree at every angle in their domain.
Pythagorean identity
sin²θ + cos²θ = 1
Secant form
1 + tan²θ = sec²θ
Double angle
sin 2θ = 2 sin θ cos θ
No. It only supports it. A proof requires algebra valid for all angles, though a single disagreement does disprove it.
Floating-point arithmetic rounds each operation, so exact identities can differ in the last few digits; a tolerance of 10⁻⁹ absorbs that.