\\( u=x^{13} \\), then \\( \\int x^{12} \\sin \\left(x^{13}\ ight) d x=\\int \\sin (u)\\left(\\frac{1}{13} d u\ ight)=\\frac{1}{13} \\int \\sin (u) d u \\) aluates as \\( \\frac{1}{13} \\int \\sin (u) d u=\\frac{1}{13}(\\quad)+C \\)