The diagonal length of the door is 1 foot = 10 foot.
According to Pythagorean Theorem: x 2+(x+6.8) 2 = 10 2.
Finishing: x 2+6.8x-26.88 = 0
x = {-6.8 √[6.8^-4× 1×(-26.88)}/2
Solution: x=-9.6 (truncation)
x=2.8
The width of the door is 2.8 feet. The door is 9.6 feet high.
That's it, there's nothing more detailed!