Green's Theorem Area Formula
Area of $R=\frac{1}{2} \oint_{C} x d y-y d x$
Use the Green's Theorem area formula given above to find the areas of the regions enclosed by the curves.
The ellipse $\mathbf{r}(t)=(a \cos t) \mathbf{i}+(b \sin t) \mathbf{j}, \quad 0 \leq t \leq 2 \pi$