{a*[sin(θ/3)]^3}' = a*{[sin(θ/3)]^3}' = a*3*[sin(θ/3)]^2 * [sin(θ/3)]' = a*3*[sin(θ/3)]^2 * (1/3)*cos(θ/3)
= a*[sin(θ/3)]^2 * cos(θ/3)
所以:{a*[sin(θ/3)]^3}^2 + {{a*[sin(θ/3)]^3}' }^2
= {a*[sin(θ/3)]^2}^2 * [sin(θ/3)]^2+ {a*[sin(θ/3)]^2}^2 * [cos(θ/3)]^2
= {a*[sin(θ/3)]^2}^2 * {[sin(θ/3)]^2 + [cos(θ/3)]^2}
= {a*[sin(θ/3)]^2}^2
这是指数运算的问题 a^m=b,那么a=b^(1/m)