skill

(1) trigonometric functions with the same angle have the law of knowing one and finding three, which can be solved by formulas. The best way is to draw a right triangle to solve it quickly.

(2) When using the above formula to calculate the trigonometric function value, we should pay attention to the correct choice of "addition and subtraction" sign in combination with the angle range.

02

Inductive formula formula formula

Odd couples, symbols look at quadrants.

To simplify by inductive formula, it is generally changed into a form first, and then simplified by inductive formula (if the front angle is an odd multiple of 90 degrees, it is "odd", and an even multiple of 90 degrees is "even"; The symbol depends on the quadrant, that is, α is regarded as an acute angle, which quadrant the angle is in, and whether the symbol of trigonometric function is "+"or "-"is added in front of this quadrant).

When calculating by inductive formula, generally, the negative angle is changed into positive angle first, then the positive angle is changed into the angle of the interval (0,360), then into the angle of the interval (0,0 180), and then into the angle of the interval (0,90).

03

Formula of sum angle and difference angle

04

Double angle formula

05

Reverse use and change of formula

06

Unit deformation (auxiliary angle formula)

Convert the sum or difference of two trigonometric functions into "one trigonometric function, one angle, one power"

Form.

, in which

07

General formula of trigonometric function

08

"sum-difference integral" and "sum-difference integral"