The perimeter is 18+18+20+20=76. 18 square root 2 /2= 12.727. Hypotenuse or triangle is 18 + 12.727+12.727=43.455. 76.18+43.455=119.635. The area is 18x20=360. (12.727x12.727)/2= 161.9765. 161.9765+360= 521.9765.
For the hypotenuse since it is a 45,45,90 triangle the two side lengths are are same so it is x square root 2 divide by 2. Hope that helps!!
