What is Pythagoras triplet?

Answer 1

It's a set of three numbers that could be the lengths of the sides of a right triangle.

In order for them to work that way, the squares of the two smaller ones have to

add up to the square of the largest one.

Answer 2

D^(2) = a^(2) + b^(2) + c^(2)

It is used to find the internal diagonal of a cube/cuboid.