誘導(dǎo)公式
sin(π+α)=-sinα
cos(π+α)=-cosα
sin(-α)=-sinα
cos(-α)=cosα
sin(2π-α)=-sinα
cos(2π-α)=cosα
sin(π-α)=sinα
cos(π-α)=-cosα
sin(π/2+α)=cosα
sin(π/2-α)=cosα
sin(3π/2+α)=-cosα
sin(3π/2-α)=-cosα
cos(π/2+α)=-sinα
cos(π/2-α)=sinα
sin^2α+cos^2α=1
csc^2α-cot^2α=1
sec^2α-tan^2α=1
tanα=sinα/cosα
cotα=cosα/sinα
sinα*cscα=1
cosα*secα=1
tanα*cotα=1
輔助角公式
asint+bcost=(a^2+b^2)^(1/2)sin(t+r)
cosr=a/[(a^2+b^2)^(1/2)]
sinr=b/[(a^2+b^2)^(1/2)]
積化和差
sina*cosb=[sin(a+b)+sin(a-b)]/2
cosa*sinb=[sin(a+b)-sin(a-b)]/2
cosa*cosb=[cos(a+b)+cos(a-b)]/2
sina*sinb=-[cos(a+b)-cos(a-b)]/2
和差化積
sina+sinb=2sin[(a+b)/2]cos[(a-b)/2]
sina-sinb=2sin[(a-b)/2]cos[(a+b)/2]
cosa+cosb=2cos[(a+b)/2]cos[(a-b)/2]
cosa-cosb=-2sin[(a+b)/2]sin[(a-b)/2]