Differential Equations

$\cos \left(\frac{y}{x}\right)=\log |x|+C$

$\cos \left(\frac{y}{x}\right)=\frac{1}{x}+C$

$\cos \left(\frac{x}{y}\right)=\log |y|+C$

$\cos \frac{y}{x}=\frac{2}{x}+C$