tanX=sinX/cosX

There are six inductive formulas, each containing a sin, a cos and a tan, totaling *** 18.

The sum and difference formula of angles, sin (ab) = sina.cosbcosa.sinb.

Cos (a b) = COSA。 COSB ganxinlang

Tan (a b) = (tana tanb)/ 1 dry tana tanb.

Double angle formula: sin2x=2sinX.cosX

cos2x=(cosx)^2-(sinx)^2=(cosx)^2- 1= 1-(sinx)^2

tan2x=2tanX/ 1-(tanX)^2

The problem of trigonometric function is basically the repeated use of the above formula. Basically, remember trigonometric functions of special angles, such as 30 degrees, 60 degrees and 45 degrees.