Topics are presented in an order so that new concepts are introduced and relevant formulas are derived in ways arising naturally in the treatment rather than by appealing to unfamiliar concepts or ud hoc methods. Modern notation and terminology are used in a geometric and algebraic approach. Some concepts of group theory are introduced and are related to this approach, but knowledge of group theory is not required. Those who plan to use continuous groups that are more abstract than the rotation group may thereby develop their insight and skills by practicing with rotations. I try to distinguish carefully results that depend only on rotational symmetry and are generally valid from those having their most fruitful interpretation from the viewpoint of quantum mechanics. Applications to quantum mechanics therefore usually appear toward the end of sections and chapters.
