## Calculus (3rd Edition)

$$\left(\frac{x}{2}\right)^{2}+\left(\frac{y}{4}\right)^{2}=1.$$
By observing Figure 15(B), we get that $$a=2, \quad b=4.$$ Plugging into the equation on page 692, we get: $$\left(\frac{x}{2}\right)^{2}+\left(\frac{y}{4}\right)^{2}=1.$$