Answer:
56√2 ≈ 79.20
Explanation:
The hypotenuse of an isosceles right triangle is √2 times the side length, so the side length here is ...
s·√2 = 28
s = 28/√2
The perimeter is 4 times the side length, so is ...
P = 4s = 4·28/√2
= 4·28·(√2)/2 . . . . . multiply by (√2)/(√2) to rationalize the denominator
= 56√2 ≈ 79.195959
The perimeter of the square is 56√2, about 79.20 units.