Opposite side/hypotenuse of sinα=∞α

Adjacent edge/hypotenuse of cosα=∞α

Opposite side of tanα = adjacent side of ∠ α/∠α.

Adjacent side of cotα = opposite side of ∠ α/∠α.

Double angle formula

Sin2A=2SinA？ Kosa

Cos2A=CosA？ -Sina? = 1-2SinA？ =2CosA？ - 1

tan2A=(2tanA)/( 1-tanA？ )

(Note: Sina? Is the square of Sina, sin2(A))

Triple angle formula

sin3α=4sinα sin(π/3+α)sin(π/3-α)

cos3α=4cosα cos(π/3+α)cos(π/3-α)

tan3a=tana tan(π/3+a) tan(π/3-a)

Derivation of triple angle formula

sin3a = sin(2a+a)= sin 2 acosa+cos 2 asina

Auxiliary angle formula of trigonometric function

Asinα+Bcosα=(A？ +B？ )' (1/2)sin(α+t), where

sint=B/(A？ +B？ )'( 1/2)

Cost =A/(A? +B？ )'( 1/2)

tant=B/A

Asinα+Bcosα=(A？ +B？ )'( 1/2)cos(α-t)，tant=A/B

Reduced power formula

Sin? (α)=( 1-cos(2α))/2 = versin(2α)/2

Because? (α)=( 1+cos(2α))/2 = covers(2α)/2

Tan? (α)=( 1-cos(2α))/( 1+cos(2α))