cot(α+k 360 )=cotα (k∈Z)，？ sec(α+k 360 )=secα？ (k∈Z), csc(α+k 360 )=cscα (k∈Z). Others are:

sin (α+k 360 )=sinα(k∈Z)

cos(α+k 360 )=cosα(k∈Z)

tan (α+k 360 )=tanα(k∈Z)

Trigonometric function is one of the basic elementary functions, which takes the angle (the most commonly used radian system in mathematics, the same below) as the independent variable, and the angle corresponds to the coordinates where the terminal edge of any angle intersects with the unit circle or its ratio as the dependent variable. It can also be equivalently defined as the lengths of various line segments related to the unit circle.

Application of inductive formula;

General steps of transforming trigonometric functions by induction;

(1) remembers the trigonometric function value of a special angle.

② Pay attention to the flexible application of inductive formulas.

③ The requirements of trigonometric function simplification are the least number of terms, the least number of times, the least function name, the simplest denominator and the best evaluation.