FourierCosCoefficient

FourierCosCoefficient[expr,t,n] gives the nth coefficient in the Fourier cosine series expansion of expr.

FourierCosCoefficient[expr,{t1,t2,…},{n1,n2,…}] gives a multidimensional Fourier cosine coefficient.

Examples

Find the first Fourier cosine coefficient:

FourierCosCoefficient[t^2, t, 1]
(* -4/Pi^2 *)

Compute higher-order coefficients:

FourierCosCoefficient[Sin[t]^2, t, 2]
(* -1/2 *)

Please visit the official Wolfram Language Reference for more details.