matplotlib多张子图画在一起

import matplotlib.pyplot as plt
import numpy as np
import math
plt.rcParams['font.sans-serif']=['SimHei'] # 用来正常显示中文标签
plt.rcParams['axes.unicode_minus']=False # 用来正常显示负号

x = np.linspace(-math.pi, math.pi)
y1 = np.sin(x)
y2 = np.cos(x)
y3 = np.tan(x)

fig=plt.figure(figsize=(12,8))
plt.figure(1)
ax1 =