# Proof that every real function has negative frequency component

I want to know why every real function has negative frequency component. If I am not correct, can anyone tell me how it is really?

I heard that it is related to Fourier analysis, though not sure.

By the way, I am a high schooler graduating next year. I understand introductory calculus (calculus I, II, III in university level), so I do not think there will be any problem for me to understand explanation.

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What does "negative frequency component" mean? – Chris Eagle Oct 10 '12 at 8:44
Google Hermitian symmetry of Fourier transform of real functions – chaohuang Oct 10 '12 at 9:11