Let α be an arbitrary angle, and the relationship between π+α and the trigonometric function value of α is sin(π+α)=-sinα, cos(π+α)=-cosα, tan(π+α)=tanα, and cot(π+α)=cotα.

The relationship between the trigonometric function values of any angle α and-α: sin(-α)=-sinα, cos(-α)=cosα, tan(-α)=-tanα, and cot(-α)=-cotα.

Using formula 1 and formula 3, we can get the relationship between the trigonometric function values of 2π-α and α: sin(2π-α)=-sinα, cos(2π-α)=cosα, tan(2π-α)=-tanα, and cot(2π-α)=-cotα.

The relationship between π/2 α and 3 π/2 α and α trigonometric function values: sin(π/2+α)=cosα, cos(π/2+α)=-sinα, tan(π/2+α)=-cotα, cot (π/2+α) =-.