1、两角和公式
sin(A+B) = sinAcosB+cosAsinB
sin(A-B) = sinAcosB-cosAsinB
cos(A+B) = cosAcosB-sinAsinB
cos(A-B) = cosAcosB+sinAsinB
2、倍角公式
Sin2A=2SinA•CosA
Cos2A = Cos2A-Sin2A=2Cos2A-1=1-2sin2A
积化和差
Sina sinb = -[cos(a+b)-cos(a-b)]
Cosa cosb = [cos(a+b)+cos(a-b)]
Sina cosb = [sin(a+b)+sin(a-b)]
Cosa sinb = [sin(a+b)-sin(a-b)]
3、诱导公式
sin(π-a) = sina
cos(π-a) = -cosa
sin(π+a) = -sina
cos(π+a) = -cosa
