Question 618749
You didn't give the number of feet but I can help you solve the problem.

If it is a square you are trying to find the distance from a corner to the opposite corner. Which means that the line is the hypotenuse of a triangle with two equal sides on either side of the 90 degrees.

So if the side is x feet then the way to find the length that you need (lets call it y) you use the formula (Pythagorus theorem):

{{{y^2 = x^2 + x^2}}} obviously if the two sides on each side of the right-angle were different then one of the x's would be different from the other, but in this case they are the same. 

so simplified {{{y^2 = 2x^2}}}

so you would square the length then times by two. Then you you find the square root to find y.