This image was acquired from
wikimedia. It was marked as Public Domain or CC0 and is free to use. To verify, go to the source and check the information there.
Keywords from Image Description:
Fourier series and transform. en Function in red is an approximation of square wave formed from just sine functions of different amplitudes and harmonicallyrelated frequencies Their summation is called Fourier series The Fourier transform in blue which depicts amplitude vs frequency reveals the frequencies and their amplitudes