# Proving Pythagorean theorem

• Sep 23rd 2009, 06:18 AM
imuthis
Proving Pythagorean theorem
Good day! Im a noob in math so i just want to ask this simple question. I know that Pythagorean theorem is the sum of the areas of 2 squares on the legs equals to the area of the square on the hypotenuse. My question is; why did they refer to a square to prove the a theorem that is being used into a triangle? thanks in advance.
• Sep 23rd 2009, 07:20 AM
rowe
Pythagoras' states: $\displaystyle c^2 = a^2 + b^2$. If we want to obtain the hypotenuse, c, we need to take squares on both sides. It's just inherent in the definition of the hypotenuse:

$\displaystyle c = \sqrt{a^2 + b^2}$
• Sep 23rd 2009, 03:08 PM
awkward
Quote:

Originally Posted by imuthis
Good day! Im a noob in math so i just want to ask this simple question. I know that Pythagorean theorem is the sum of the areas of 2 squares on the legs equals to the area of the square on the hypotenuse. My question is; why did they refer to a square to prove the a theorem that is being used into a triangle? thanks in advance.

You can find several proofs of the theorem here:

Pythagorean theorem - Wikipedia, the free encyclopedia

(My personal favorite is the one titled "Algebraic Proof".)
• Sep 23rd 2009, 08:25 PM
imuthis
I read all about that in wikipedia and even watch videos in you tube but i dont get it, why they are trying to prove an equation for a triangle using a square.
• Sep 24th 2009, 11:42 AM
rowe
Quote:

Originally Posted by imuthis
I read all about that in wikipedia and even watch videos in you tube but i dont get it, why they are trying to prove an equation for a triangle using a square.

We don't have to use this method of proof, as awkward has pointed out, there are many proofs of the theorem. It just so happens that the proof you mention is a popular and simple one. If you still want to worry about it, think about how a right-angled triangle relates to a rectangle/square. Could a square be built out of triangles, and vice-versa?
• Sep 24th 2009, 08:07 PM
imuthis
Thanks masters you really point me to the right direction! Ill just have to work on this a liitle bit more to prove the relationship. Thanks again!