tan sin cos 一些有关的式子？

sin(x+y)=sinxcosy+cosxsiny

sin(x-y)=sinxcosy-cosxsiny

cos(x+y)=cosxcosy-sinxsiny

cos(x-y)=cosxcosy+sinxsiny

tan(x+y)=(tanx+tany)/(1-tanxtany)

tan(x-y)=(tanx-tany)/(1+tanxtany)

sin(-x)=-sinx cos(-x)=cosx tan(-x)=-tanx

cot(-x)=-cotx sec(-x)=secx csc(-x)=-cscx

tanx=sinx/cosx cotx=cosx/sinx

tanxcotx=1 tanx+cotx=1/(sinxcosx)

secx=1/cosx cscx=1/sinx

1+(tanx)^2=1/(cosx)^2=(secx)^2

1+(cotx)^2=1/(sinx)^2=(cscx)^2

sin2x=2sinxcosx

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

sin3x=-(sinx)^3+3sinx(cosx)^2

cos3x=(cosx)^3-3cosx(sinx)^2

(sinx)^2+(cosx)^2=1

tan(x/2)=(1-cosx)/sinx=sinx/(1+cosx)

和差化积(积化和差):

sinx+siny=2sin((x+y)/2)cos((x-y)/2)

sinx-siny=2cos((x+y)/2)sin((x-y)/2)

cox+cosy=2cos((x+y)/2)cos((x-y)/2)

cox-cosy=-2sin((x+y)/2)sin((x-y)/2)