Pythagoras, with alternative proofs from lots of others.
pythagoras made the famous pythagoras theorem and many more....
Pythagoras theorem
To know about Pythagoras theorem in detail
For a number of proofs see: http://www.cut-the-knot.org/pythagoras/ Proof 6 seems to be the most straightforward.
There are 19 various aspects of Pythagoras theorem. Pythagorean Theorem (1) Pythagoras Theorem(2) Pythagorean Theorem (3) Pythagorean Theorem (4) Pythagoras Theorem(5) Pythagorean Theorem(6) Pythagrean Theorem(7) Pythagoras Theorem(8) Pythagorean Theorem (9) Hyppocrates' lunar Minimum Distance Shortest Distance Quadrangular Pyramid (1) Quadrangular Pyramid (2) Origami Two Poles Pythagoras Tree(1) Pythagoras Tree(2) Theorem by Pappus
Pythagoras' theorem is applicable to right angle triangles
~The Pythagoras theorem
Well, there are many, many proofs of the Pythagorean Theorem. Some sources have as many as 93 proofs. Here is my favorite, but others are listed in the math website in Related Links (below).This is an excerpt from a letter by Dr. Scott Brodie from the Mount Sinai School of Medicine, NY, taken from the first website, proof # 21.The first proof I merely pass on from the excellent discussion in the Project Mathematics series, based on Ptolemy's theorem on quadrilaterals inscribed in a circle: for such quadrilaterals, the sum of the products of the lengths of the opposite sides, taken in pairs equals the product of the lengths of the two diagonals. For the case of a rectangle, this reduces immediately to a² + b² = c².Related LinksA website with 93 proofs of the Pythagorean Theorem. http://www.cut-the-knot.org/pythagoras/index.shtmlAn award-winning applet that demonstrates one of the most famous proofs of the Pythagorean Theorem. http://www.cut-the-knot.org/pythagoras/morey.shtml
It is Pythagoras' theorem
look in google if not there, look in wikipedia. fundamental theorem of algebra and their proofs
There are a great number of different proofs of the Pythagorean Theorem. Unfortunately, many of them require diagrams which are hard to reproduce here. Check out the link to Wikipedia's page on the theorem for several different proofs.