In order to use the pythagorean theorem to find the magnitude of a resultant vector, which must be true regarding the two initial vectors?

the skeletons of most mammals reach a certain size and then stop growing. however, many animals, including some mammals, keep growing throughout their lives. kangaroos, for example, just keep growing and growing until they die. also, the longer an animal lives the greater the chance it might catch some deadly disease.

snell's law

refractve index = sin incidence / sin refraction