sin^2(2x)=(1-cos4x)/2,T=2π/4=π/2
这是公式：sin(ωx+φ)和cos(ωx+φ)的最小正周期T=2π/ω
T=2π/4=π/2
不懂再问哦sin^2(2x)=(1-cos4x)/2???whycos2X=cos(x+x)=(倍角公式)cosx*cosx-sinx*sinx=(cos^2)x-(sin^2)x=(cos^2)x+(sin^2)x-2(sin^2)x=1-2(sin^2)x则cos4x=1-2(sin²2)x所以(sin²2)x=(1-cos4x)/2具体三角公式最好翻书