Question

sin(a+b)-sina等于

Answer 1

sin(A+B)-sinA=2cos(A+B/2)*sinB/2的推导过程：

sin(A+B)-sinA

=sin [(A+B/2)+ B/2]-sin[(A+B/2)- B/2]

=[sin(A+B/2)cos B/2+cos(A+B/2)sin B/2]-[ sin(A+B/2)cos B/2-cos(A+B/2)sin B/2]

=2 cos(A+B/2)sin B/2

扩展资料：

积化和差公式：

sinα·cosβ=(1/2)[sin(α+β)+sin(α-β)]

cosα·sinβ=(1/2)[sin(α+β)-sin(α-β)]

cosα·cosβ=(1/2)[cos(α+β)+cos(α-β)]

sinα·sinβ=-(1/2)[cos(α+β)-cos(α-β)]

和差化积公式：

sinα+sinβ=2sin[(α+β)/2]cos[(α-β)/2]

sinα-sinβ=2cos[(α+β)/2]sin[(α-β)/2]

cosα+cosβ=2cos[(α+β)/2]cos[(α-β)/2]

cosα-cosβ=-2sin[(α+β)/2]sin[(α-β)/2]