FourierCoefficient

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

• FourierCoefficient[expr, {t1, t2, ...}, {n1, n2, ...}] gives a multidimensional Fourier coefficient.

Examples

Compute the 3rd Fourier coefficient:

FourierCoefficient[Cos[3 t], t, 3]

Get Fourier coefficients for a square wave:

FourierCoefficient[SquareWave[t], t, 1]

Please visit the official Wolfram Language Reference for more details.