The window is in the shape of an equilateral triangle.

Side of the triangle $\"\"$ feet.

Draw the related equilateral triangle for the problem.

Let $\"\"$ be the length of the support.

$\"\"$

Pythagoras theorem: Square of the hypotenuse is equal to the sum of the other two sides.

$\"\"$ .

Solve for $\"\"$ .

$\"\"$

Take square root each side.

$\"\"$

Since length is always positive, $\"\"$ .

Length of the support is $\"\"$ ft.

Option G is correct.