Question

как найти dy/dx если y=x*cos(альфа)

Answer 1

$y=xcos alpha \ y'=cos alpha$

$y=xcos alpha =>x= frac{y}{cos alpha } \ x'= frac{1}{cos alpha }$


$frac{dy}{dx} = frac{y'}{x'} = frac{cos alpha }{ frac{1}{cos alpha } } =cos^2 alpha$