Answer
15.6in
Work Step by Step
Step 1. Assume the window has a standard ellipse equation $\frac{x^2}{a^2} +\frac{y^2}{b^2}=1, y\geq0 $
Step 2. Use the figure given in the Exercise, we have $2a=80in$ thus $a=40in$, and $b=20in$, which gives the equation as $\frac{x^2}{40^2} +\frac{y^2}{20^2}=1, y\geq0 $
Step 3. At $x=25in$, we have $\frac{25^2}{40^2} +\frac{y^2}{20^2}=1 $ which leads to $h=y\approx15.6in$
