Let α be an arbitrary angle, and the values of the same trigonometric function with the same angle of the terminal edge are equal:

sin(2kπ+α)= sinα

cos(2kπ+α)= cosα

tan(2kπ+α)= tanα

cot(2kπ+α)= cotα

Equation 2:

Let α be an arbitrary angle, and the relationship between the trigonometric function value of π+α and the trigonometric function value of α;

Sine (π+α) =-Sine α

cos(π+α)= -cosα

tan(π+α)= tanα

cot(π+α)= cotα

Formula 3:

The relationship between arbitrary angle α and the value of-α trigonometric function;

Sine (-α) =-Sine α

cos(-α)= cosα

tan(-α)= -tanα

Kurt (-α) =-Kurt α

Equation 4:

The relationship between π-α and the trigonometric function value of α can be obtained by Formula 2 and Formula 3:

Sine (π-α) = Sine α

cos(π-α)= -cosα

tan(π-α)= -tanα

cot(π-α)=-coα

Formula 5:

The relationship between the trigonometric function values of 2π-α and α can be obtained by Formula-and Formula 3:

Sine (2π-α)=- Sine α

cos(2π-α)= cosα

tan(2π-α)= -tanα

Kurt (2π-α)=- Kurt α

Equation 6:

The relationship between π/2 α 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)= -tanα

sin(π/2-α)= cosα

cos(π/2-α)= sinα

tan(π/2-α)= cotα

cot(π/2-α)= tanα

sin(3π/2+α)= -cosα

cos(3π/2+α)= sinα

tan(3π/2+α)= -cotα

cot(3π/2+α)= -tanα

sin(3π/2-α)= -cosα

cos(3π/2-α)= -sinα

tan(3π/2-α)= cotα

cot(3π/2-α)= tanα

(higher than k∈Z)