Ancient Egyptians were able to create right angles for building and surveying using a rope with 12 equally-spaced knots to form a right triangle.

Any triangle can be cut and reformed into a rectangle.

The two smaller numbers of a Pythagorean triple cannot both be odd.

Any multiple of a Pythagorean triple is also a Pythagorean triple.

The Pythagorean Theorem holds for any numbers a, b, and c that form
the sides of a right triangle.

If two right triangles have corresponding sides the same length, the triangles have to be the same size and shape (congruent).

This diagram shows that (a + b)² = a² + 2ab + b²