Let A, B, and C be points in a plane, and C be the midpoint of AB.

Then, if AB is a segment, and D be the midpoint of BC, then AD = BD = CD = (1/2)AB.

Read the next one, it's not that hard.

Proof 2: The One Where We Use a Triangle

In a triangle with sides a, b, and c, and a right angle at vertex C, then a^2 = b^2 + c^2.

And then there's the next one, because this one was too easy.

Proof 3: The One with the Similar Triangles

Let A and B be two triangles with sides a, b, and c, and d, e, and f. Then, if ABC and DEF are similar, then a^2 = d^2.

And don't even get me started on the next one, it's a real doozy.

Proof 4: The One with the Algebra

Let x be a real number, then x^2 = x^2.

And then we have the one with the fancy calculus.

Proof 5: The One with the Fancy Calculus

Let's just say that it's obvious, okay?

And finally, the one with the answer.

Proof 6: The One with the Answer

a^2 = b^2 + c^2, duh.