说明：  1、利用Matlab求观察图示周期三角脉冲的傅里叶级数与原波形的关系。要求分别画出最高谐波次数n=1，3，5，7时合成波形与原波形的对照图。
(The relationship between the Fourier series of the graphic periodic triangular pulse and the original waveform is observed by Matlab. The comparison of the synthetic and original waveforms at the highest harmonic frequency of n=1, 3, 5, and 7 is required)