函数f(x)=2sinxcosx-2cos²x+1,1.若f（θ)=3/5,求cos2（π/4-2θ）的值解析：f(x)=2sinxcosx-2cos²x+1=sin2x-cos2x=√2sin(2x-π/4)∵f(θ)=√2sin(2θ-π/4)=3/5==> sin(2θ-π/4)=3√2/10∴sin(π/4-2θ)...