∵ sin(X-π/4）=√2/4∴ sinx*sin(π/4)-cosx*cos(π/4)=√2/4∴ sinx*(√2/2)-cosx*(√2/2)=√2/4∴ sinx-cosx=1/2∴ (sinx-cosx)²=1/4∴ sin²x+cos²x-2sinxcosx=1/4∴ 1-2sinxcosx=1/4∴ sinxcosx...