The question (with solution) and my work are both uploaded (Question #11).

I know I can find the b_n values using the summation for cos(x) and I know I must find the a_n values by solving for the Cauchy products for each successive c_n value but I do not know how to obtain the c_n values so that I can find the a_n values.

Any help in solving this problem would be greatly appreciated!

Thanks in advance