The side of the square = 42/sqrt 2 inches
So.....the number of feet of trim needed = 4 * 42 / sqrt 2 ≈ 118.8 inches = 118.8/12 = 9.9 ft
The sq ft of glass needed = 4 * (1/2) 21^2 = 2 * 21^2 = 882 sq in = 882/12^2 = 6.125 ft^2
