1. Note that angle variables are only defined to within a modulus. Thus, if q3 were an angle variable,Wcould not be proportional to q3. However,Wcould be proportional to sin (q3).
2. P. M. Morse and H. Feshbach,Methods of Theoretical Physics(McGraw-Hill Book Company, Inc., New York, 1955), Vol. I, p. 291.
3. L. I. Schiff,Quantum Mechanics(McGraw-Hill Book Company, Inc., New York, 1955), 2nd ed., p. 140.