The square is formed by 2 right triangles, where 20 is the hypotenuse.
We can apply the Pythagorean theorem:
c^2 = a^2 + b^2
Where:
c = hypotenuse = 20
a & b = the other 2 legs of the triangle = s
Since a square has 4 equal sides s, both legs of the triangle are the same (s)
Replacing:
20^2 = s^2+s^2
Solve for s
20^2 = 2 s^2
20^2 = 2 s^2
400 = 2 s^2
400/2 = s^2
200 = s^2
√200 = s
√(2 x 100 ) = s
√2 √100 = s
10 √2 = s
