Answer:
diagonal of square = d = 9.899
Explanation:
let side of square = x
diagonal of square = d
perimeter = P = 28
4 * x = P
x = 28/7
x = 7
By using Pythagorean theorem we get
x^2 + x^2 = d^2
7^2 + 7^2 = d^2
d^2 = 98
d = sqrt(98)
diagonal of square = d = 9.899