Answer:
Supposed that you needed to know the diagonal distance from opposite corners of a rectangular prism.
d^2=x^2+y^2+z^2 where x, y, and z are the dimensions of the prism, or rectangular "box"
If the box has a width of 10, depth of 20, and a height of 30 then you have:
d^2=100+400+900
d^2=1400
d^2=100*14
d=ā(100*14)
d=10ā14 units
dā37.42 units (to nearest hundredth of a unit)
You might need this information to determine the most amount of space necessary to allow this box to pass through in any orientation...as the diagonal is the maximum dimension of the box.
I did a three-dimensional problem as the Pythagorean Theorem is often used only for two-dimensional problems in early mathematics.