Answer:
12.57 ft
Explanation:
First thing we need to find is the radius of the circular glass pane. We are given the information that the center of the glass plane is directly in the center of the triangle and that the closest distance from the center to the roof is 3 ft, including a metal border with a width of 1 ft.
Since the metal frame is the same width all the way around the window, we can safely conclude that the radius of the circular glass pane is 2 ft, as the 3ft measurement included the radius and the metal frame.
Now that we have our radius we can use the formula:
(Circumference = 2 x pi x radius)
Using 3.14 for pi we get:

or 12.57 ft (2.d.p)