Question

F(x)=cos3x/x производная

Answer 1

$f'(x)=( frac{cos3x}{x} )'= frac{(cos3x)'*x-x'*cos3x}{ x^{2} } = frac{-sin3x*(3x)'*x-cos3x}{ x^{2} } =$
$=- frac{x*sin3x+cos3x}{ x^{2} }$