(sinX+sinθ) .(Sinx-sinθ)=sin(x+θ).cos(x-θ)证明

(sinX+sinθ) .(Sinx-sinθ)=sin(x+θ).cos(x-θ)证明 化简cosθsinx-sin(x-θ)+(tanθ-2)sinx-sinθ 证明成立：[cos(3x)-sin(3x)]/(cosx+sinx)=1-2sin(2x). 证明sin(x+y)sin(x-y)=sinx-siny F(x)=sin^2θsinx+cos^2θcosx 谁能帮我化简一下? 证明 [sin(2x+y)/sinx]-2cos(x+y)=siny/sinx 证明x∈(0,π/2),cos(cosx)>sin(sinx) 证明等式：[cos(3x)-sin(3x)]/(cosx+sinx)=1-2sin(2x).成立 证明sinx+siny+sinz-sin(x+y+z)=4sin((x+y)/2)sin((x+y)/2)sin((x+ sin(x+△x)-sinx=2sin△x/2.cos(x+△x/2) sin(x+y)-sinx=2cos(x+1/2y）sin(1/2y)的详细证明步骤. sinx+cosx/sinx-cosx=2 求sinx/cos^3x +cosx/sin^3x