1. Basic conclusions of Fourier transform
(1) Triangular form: Any function can be expressed by a triangular formula (infinitely multiple accumulation, from 1 to infinity)
(2) Plural form: a relationship between trigonometric functions and complex numbers: cosx= (E^ix+e^-ix)/2 sinx= (E^ix-e^-ix)/2 (Euler's formula)
So
(3) Fourier transform
"Related reading:
1. The origin of Fourier transform and the formula of Fourier transform under complex numbers proves
2. Derivation of Fourier transform (there is a problem with the original document layout-This is a revised version)
3. Fourier transform, if you don't understand the text, just come and strangle me. "Full Version"
4. The purpose of Fourier transform: To convert the range into the frequency domain, although the signal in the range is variable, but in the frequency domain is a regular, that is, a fixed number of constant frequency domain values (such as sin cos function).
5. Fourier transform (Encyclopedia)
6. Discrete Fourier transform (encyclopedia)
7. Fast Fourier transform (encyclopedia)
Fourier transform detailed