1.f(x)=sinx/2-2cosx/2=0 可得sin(x/2)=2cos(x/2),所以tan(x/2)=(sinx/2)/(cosx/2)=1/2所以tanx=(2tanx/2)/[1-tan(x/2)^2]=4/3.2.分子cos2x=(cosx)^2-(sinx)^2=(sinx+cosx)(sinx-cosx)分母=√2(cosxcosπ/4-sinxsin...