MaplePrimes - answers and comments on Question, Extracting Coefficients from a Fourier Series

A way

Preben Alsholm — Thu, 24 Jan 2013 04:53:32 Z

restart;
u:=A*sin(x)*cos(z) + B*sin(2*x)*cos(z) + C*sin(3*x)*cos(2*z);
L:=convert(u,list);
eval(L,{sin=1,cos=1});
L/~%;

All assuming that sine or cosine don't appear in the coefficients.

Carl Love — Thu, 24 Jan 2013 05:02:50 Z

Just apply coeff twice:

S:= A*sin(x)*cos(z) + B*sin(2*x)*cos(z) + C*sin(3*x)*cos(2*z):

coeff(coeff(S, sin(2*x)), cos(z));