>>423
arccos(x^3)=y
x^3=cosy
x=(cosy)^(1/3)
dx/dy=-1/3(cosy)^(-2/3)siny
dx/dy=-siny/{3(cos^2y)^(1/3)}
dy/dx=-{3(cos^2y)^(1/3)}/siny
dy/dx=-{3(x^6)^(1/3)}/√(1-x^6)
dy/dx=-3x^2/√(1-x^6)
{arccos(x^3)}'=-3x^2/√(1-x^6)