When I teach about vectors, I find that I often have to pull from a few different sources. Some methods for solving vectors such as using Trig functions and the Pythagorean theorem are found directly in regents review books, but in order to elevate my students' knowledge of vectors, I want them to be able to solve for the resultant of more than just two vectors at a time. Also, vectors at right angles to each other isn't much of a challenge is it?
I remember being troubled at how much trigonome