beautiful math demonstrations

[cyclops]

You mean two flips to make a rotation, right?

My proof is so beautiful; it deserves better explanation.
So let M, the center of the circle, lie on AB. A, B and C on the circle.
Get your scissors and cut out triangle ABC. Fold MA on MC and MB on MC. Rub it flat. You are left with a rectangle.

[flOvermind]

I honestly don't see why you should get a rectangle (that is, without the prior knowledge that the angle is 90 degrees )...

[bayu]

I honestly don't see why you should get a rectangle (that is, without the prior knowledge that the angle is 90 degrees )...

Proof by staring

The other three angles are automatically 90 degrees

two of them due to symmetry (folding an isocele triangle in half) the other one because you folded a 180 degree angle in half

hence, so is the fourth one.

Great proof!

[flOvermind]

Ah, I missed that. Nice proof indeed

[cyclops]

As usual I was too terse. Now for some other nice proofs.
The proof that no rational squares to 2; that e doesn't solve a rational polynomial equation.
And the impossibilities: By construction: trisect an angle, double a cube, measure pi.
The non existence of a formula solving a general polynomial equation of degree higher than 4.