中文说明：让我们明白FFT。它是快速傅立叶变换的算法来计算DFT或离散傅立叶变换的快速和有效的方式。究竟是什么过滤。我们怎样才能筛选简单的方式的信号。什么是FFT的这种对称特性和更重要的是了解有关FFT的核心事实。首先让我们为50Hz构建一个简单的正弦信号的幅度=5。我正在考虑的100倍消息的频率采样频率（这应该是至少两倍票面Nequist率），这意味着我将收集1000个样本，从实际的模拟正弦信号。因此，如果频率为50，这意味着你会得到一个样品在1/50或0.02秒。如果你想10个样品，你要收集样品0.2秒。你会在每1/5000秒采样信号。
English Description：
Let us understand FFT. It is Fast Fourier Transform, an algorithm to calculate DFT or discrete fourier transform in fast and efficient way.what exactly is filtering. How can we filter a signal in simple way. What is this symmetrical features of FFT and more importantly understanding the core facts about FFT.First Let us construct a simple sinusoidal signal of 50Hz with amplitude=5. I am considering a sampling frequency of 100 times the message frequency(it should it least be twice as par Nequist rate), which means I will collect 1000 samples from the actual analog sinusoidal signal. So if the frequency is 50, that means you will get one sample at 1/50 or .02 seconds. If you want 10 samples, you have to gather the samples for .2 seconds. You will sample the signal at every 1/5000 seconds.