Formula 1: The values of the same trigonometric functions of the angles of the same terminal edge are equal.

Let α be an arbitrary acute angle, and the expression of this angle in the arc system is:

sin(2kπ+α)=sinα(k∈Z)

cos(2kπ+α)=cosα(k∈Z)

tan(2kπ+α)=tanα(k∈Z)

cot(2kπ+α)=cotα(k∈Z)

Equation 2: Relationship between trigonometric function value of π+α and trigonometric function value of α.

Let α be an arbitrary angle, and the expression of this angle in the arc system is:

Sine (π+α) =-Sine α

cos(π+α)=-cosα

tan(π+α)=tanα

cot(π+α)=cotα

The mathematical induction formula is a trigonometric function, which transforms a trigonometric function with a large angle into a trigonometric function with a small angle by using periodicity. There are six groups of inductive formulas, 54 of which are * * *.

The trigonometric function induction formula is a mathematical formula, that is, the trigonometric function at any angle is transformed into the trigonometric function at an acute angle. Including some commonly used formulas and differential product formulas.

Derivation of general formula;

sin2α=2sinαcosα=2sinαcosα/.

(because of cos? (α)+sin？ (α)= 1)。

Then divide the fraction up and down by cos 2 (α), and you can get sin2α=2tanα/.

Then replace α with α/2.

Similarly, the universal formula of cosine can be derived. By comparing sine and cosine, a general formula of tangent can be obtained.