The following formula is mandatory:

Formula 1: Let α be an arbitrary angle, and the values of the same trigonometric functions with the same terminal angles are equal. sin(2kπ+α)=sinα(k∈Z), cos(2kπ+α)=cosα(k∈Z), tan (2kπ+α) = tanα.

Equation 2: 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.

Equation 3: the relationship between any angle α and trigonometric function value of-α: sin(-α)=-sinα, cos(-α)=cosα, tan(-α)=-tanα, and cot(-α)=-cotα.

Equation 4: Using Equation 2 and Equation 3, we can get the relationship between the trigonometric function values of π-α and α: sin(π-α)=sinα, cos(π-α)=-cosα, tan(π-α)=-tanα, and cot(π-α)=-cotα.

Equation 5: Using Equation 1 and Equation 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) =-.

Equation 6: The relationship between π/2α and 3 π/2 α and the trigonometric function value of α: sin(π/2+α)=cosα, cos(π/2+α)=-sinα, tan(π/2+α)=-cotα, cot (π/2+α) cot (.