By definition of a square, all it's sides are the same measurement (typically signified by the variable <em>s</em> on all sides).
In a triangle (as with a intersection from one corner to the other (diagonal), It would create a right triangle. Remember, the two leg sides are the same measurement (typically placed as 1). There is one triangle side measurement rule:
1 , 1 , √2
Plug in the corresponding numbers to the corresponding units. the 5 inches is a side (not the hypotenuse), so it belongs in the 1:
1 x 5 = 5
1 x 5 = 5
√2 x 5 = 5√2
The measurement of it's diagonal (hypotenuse) is 5√2.
The angles of a square are right angles. If you draw a diagonal, you'll see that it forms a right triangle. Since the sides of a square are congruent, the right triangle will be a 45-45-90 right triangle. The hypotenuse of a 45-45-90 right triangle is times the length (5) .