2017 THREE(e)

For the function $y=e^x\cos kx$:

(i) Find $\frac{dy}{dx}$ and $\frac{d^{2}y}{d{x}^2}$.

(ii) Find all the value(s) of $k$ such that the function $y=e^x\cos kx$ satisfies the equation

$\frac{d^{2}y}{d{x}^2}-2\frac{dy}{dx}+2y=0$ for all values of $x$.