Question

967 А Найдите производную функции

Answer 1

$y=sinx\cdot cos3x\\\\y'=(sinx)'\cdot cos3x+sinx\cdot (cos3x)'=cosx\cdot cos3x+sinx\cdot (-3sin3x)\\\\y'(\pi )=cos\pi \cdot cos3\pi -3sin\pi \cdot sin3\pi =-1\cdot (-1)-0=1$