Trigonometric identity transformation is a simple identity transformation using sine, cosine, tangent formula and half-angle formula of the sum and difference of two angles, which is located at the junction of trigonometric function and mathematical transformation.

Basically, inductive formulas can be derived from trigonometric function images, and other formulas can also be derived from inductive formulas, including double angle formula, sum-difference product, universal formula and so on.

Triple angle

sin3α = 3sinα-4sin？ α

cos3α = 4cos？ α-3cosα

tan3α = (3tanα-tan？ α)/( 1-3tan？ α)

sin3α = 4sinα sin(π/3-α) sin(π/3+α)

cos3α = 4cosα cos(π/3-α) cos(π/3+α)

tan3α = tanα tan(π/3-α) tan(π/3+α)