tan(x-π/4)=2,求sin2x+2cos2x/2cos^x-3sin2x-1
问题描述：
tan(x-π/4)=2,求sin2x+2cos2x/2cos^x-3sin2x-1
答
1) sin2A=2sinAcosA (2) cos2A=2(cosA)^2-1=1-2(sinA)^2 (3) tan2A=2tanA/[1-(tanA)^2] 接下来讲讲推导过程:sin2A=sin(A+A)=sinAcosA+cosAsinA=2sinAcosA cos2A=cos(A+A)=cosAcosA-sinAsinA=(cosA)^2-(sinA)^2=2(cos...