Fundamentals of Engineering Electromagnetics 1st Edition by David Cheng

تمرين 40

Let unit vectors a A and a B denote the directions of vectors A and B in the xy -plane that make angles and , respectively, with the x -axis.
a) Obtain a formula for the expansion of the cosine of the difference of two angles, cos ( ), by taking the scalar product a A · a B.
b) Obtain a formula for sin ( ) by taking the vector product a B × a A.