Chapter 8 - Geometry - 8.8 Pythagorean Theorem - 8.8 Exercises - Page 593: 40

The unknown length in the window frame is $= 5$ ft.

Let $H =$ hypotenuse of the triangle / unknown length in the window frame $a^{2} + b^{2} = c^{2}$ $4^{2} + 3^{2} = H^{2}$ $16 + 9 = H^{2}$ $25 = H^{2}$ $H = \sqrt 25$ $H = 5$ ft