Tan stands for tangent, that is, the ratio of the side corresponding to an acute angle to another right angle in a right-angled trigonometric function.

Cos means cosine, the ratio of the right side adjacent to the acute angle to the hypotenuse.

Sin means sine, corresponding to the edge of acute angle and the edge of hypotenuse.

Extended data

Basic relations of trigonometric functions with the same angle

Reciprocal relations: tanα cotα= 1+0, sin α CSC α = 1, cos α secα =1; +0;

The relationship of quotient: sinα/cosα=tanα=secα/cscα, cos α/sin α = cot α = CSC α/sec α;

And the relationship: sin2α+cos2α= 1, 1+tan2α=sec2α,1+cot2α = csc2α;

Square relation: sin? α+cos？ α= 1。

Double angle formula

sin2α=2sinαcosα

tan2α=2tanα/( 1-tan^2(α))

cos2α=cos^2(α)-sin^2(α)=2cos^2(α)- 1= 1-2sin^2(α)？

half-angle formula

sin^2(α/2)=( 1-cosα)/2

cos^2(α/2)=( 1+cosα)/2

tan^2(α/2)=( 1-cosα)/( 1+cosα)

tan(α/2)= sinα/( 1+cosα)=( 1-cosα)/sinα