Question 538105
For a square P=4s.  That means each side s=p/4 = 40/4=10.<P>
The diagonal of a square makes a right triangle with two sides.  The diameter is the hypotenuse (h) of that right triangle.<P>
Pythagorean Theory {{{h^2=s^2+s^2=2s^2}}} so {{{h = sqrt(2s^2)}}}.
Plug s=10 into that formula.<P>
{{{h=sqrt(2(10^2)) = sqrt(2*100) =10*sqrt(2)= 14.1}}} ft.

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