The Pythagorean theorem, stating that the square of the hypotenuse is equal to the sum of the squares of the sides in a right triangle, is a fundamental concept in geometry and trigonometry.

There are many, many ways to prove the Pythagorean theorem. This page contains 84 different proofs, and The Pythagorean Proposition by Loomis contains another 367 proofs.

This is what I think to be an interesting proof, by the use of two circles. It is number 89 in Loomis’s book.

Starting with a right triangle, we draw two circles:

Here, is right, and *A* and *B* are the centers of circles and respectively.

Now we draw some additional lines, extending *AB* to *F* and *G*:

In this diagram, we can prove that :

- is right. This is an application of Thales’ theorem since
*DG*is a diameter. - is right. This is given.
- . Since , .
- . This is because
*BC*and*BG*are both radii of and is isosceles. - .
- . The two triangles have two shared angles: and .

In a similar way, we can prove that .

The rest of the proof is algebraic rather than geometric. Let’s call the side *AC* to be *b*, *BC=a*, and *AB=c*.

From the similar triangles, we have the following ratios:

(or, )

(or, )

Adding the two equations, we get:

The line *BF* can be split into *AF* and *AB* which is equal to *c+b* since *AF = AC*.

The line *EB* can be considered the difference between *AB* and *AE*, which is equal to *c-b*.

Similarly, *AG = AB+BG = c+a*, and *AD = AB-DB = c-a*. By substitution:

*Q.E.D.*

please show some methods or some points by which ican prove pythagoras theorem in circles or e – mail it on my e – mail address navukappor@gmail.com

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yes i also want these points to make my project report

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thanks a lot it was very useful n easy to understand

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