Find and equation of the tangent line to the curve at the point defined by the given value of t. Also, find the value of $\displaystyle \frac{d^2y}{dx^2} $ at this point $\displaystyle x=-cos(t)$, $\displaystyle y=9+sin(t)$, $\displaystyle t=\frac{\pi}{2}$

Thanks for any help.