Image: Fourier series integral identities

Description: Sines and cosines form an orthonormal set — that is, the integral of sine, cosine and their product is equal to zero (green and red areas are equal, and cancel out) when m, n or the functions are different, and equal to pi only if m and n are equal, and the function used is the same.
Title: Fourier series integral identities
Credit: Own work
Author: Lucas Vieira
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License: Public domain
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