For the first time this Theorem was discovered by Indian Mathematicien , Baudhayan . Hence it is also known as Baudhayan's Theorem .
Egyptians also used this theorem in construction.
This is how many of the Egyptians pyramids are built.
The Egyptians wanted a perfect 90-degree angle to build the pyramids which were actually two right-angle triangle whose hypotenuse forms the edges of the pyramids.