3-4-5 triangles: If a right triangle’s leg-to-leg ratio is 3:4, or if the leg-to-hypotenuse ratio is 3:5 or
4:5, then it’s a 3-4-5 triangle, and you don’t need to use the Pythagorean theorem to find the third
side. Just figure out what multiple of 3-4-5 it is.
In the right triangle shown, one leg is 30 and the hypotenuse is 50. This is 10 times 3-4-5. The other
leg is 40.
4. The 30-60-90 Triangle