You use the Pythagorean theorem, and get 12 squared plus 12 squared equals c ( hypothenuse). So 144 plus 144 equals to radical 288. So the answer is 17.
The perimeter is the sum of the three sides. Use Pythagorean theorem to find the missing side (hypotenuse). a^2+b^2=c^2 12^2+12^2=c^2 144+144=c^2 288=c^2 Sqrt288=c 17=c P= 12+12+17 P=41 ft
