What is a right triangle similarity theorem?

Question

How to do/use?

Answer 1

In a right triangle an altitude drawn to the hypotenuse divides the triangle into two smaller triangles that are similar to each other and both are similar to the original triangle.

Answer 2

If the ratio of the corresponding sides of the triangles are proportional and satisfies the Pythagorean triple (3-4-5), then the right triangles are similar.