3. Draw vectors u and v tail-to-tail so that they make a è-degree angle. Draw the vector u − v, the third side of the triangle, and check to see that it points in the right direction.
(a) Solve for cos è using the SSS version of the Law of Cosines, expressing all lengths in terms of u, v, and u − v.
(b) If you use vector algebra to simplify the numerator as much as possible, you will
discover an interesting new result connecting u•v to cos è.