Answer
$dy=\frac{x+sinx\times cosx}{cos^{2}x} \times dx$
Work Step by Step
$y=x\times tan(x)$
$dy/dx=(x)(sec^{2}x)+(1)(tan(x))$ (derivative of tangent, product rule)
$=(\frac{x}{cos^{2}x})+(\frac{sinx}{cosx})=\frac{x+sinx\times cosx}{cos^{2}x}$
$dy=\frac{x+sinx\times cosx}{cos^{2}x} \times dx$
