Now we wish to find as and ps, which are not undetermined constants. (the requisite two undetermined con- stants already appear in zn). one strategy of proceeding involves expanding the sine and cosine functions on the left-hand-side of eq. (30) as, cos(ω t + ps.) cos(ω t) cos((ω t) sin(ps.) sin(ω t + p")-sin(ω t) cos(n.) + cos(ω t) sin(a.) using these in eq. (30) and equating coefficients of cos(32t) and sin(32t) leads to, (22- 2) sin(p)-ycos(ps)as (31) (32) ro