话不多说，直接上代码：
# -*- coding:utf-8 -*-
"""
author: 15025
time: 05.09.2021 05:27:21
software: PyCharm
Description:
we will draw four figures here.
1. draw figure of e^x and e^-x
2. draw figure of e^x / x and e^-x / x
3. draw figure of e^-x / x, e^-2x / 2x, e^-3x / 3x
4. draw figure of ln(x)
Note: In Python, np.log(x) means ln(x) in math
Comment:
For task 3, with the increase of index, the speed of decreasing is up
"""
import numpy as np
import matplotlib.pyplot as plt
import warnings # ignore divide by zero warning
war
