pyplot的文本显示

import numpy as np
import matplotlib.pyplot as plt

a = np.arange(0.0,5,0.02)
plt.plot(a,np.cos(2*np.pi*a),'r--')
plt.xlabel('横轴：时间',fontproperties='SimHei',fontsize=15,color='green')
plt.ylabel('纵轴：振幅',fontproperties='SimHei',fontsize=15)
plt.title('正弦波实例$y=cos(2\pi x)$',fontproperties='SimHei',fontsize=25)
plt.text(2,1,'$\mu=100$',fontsize=15)

plt.axis([-1,6,-2,2])
plt.grid(True)
plt.show()

 plt.annotate(s,xy=arrow_crd,xytext=text_crd,arrowprops=dict)

import numpy as np
import matplotlib.pyplot as plt

a = np.arange(0.0,5,0.02)
plt.plot(a,np.cos(2*np.pi*a),'r--')

plt.xlabel('横轴：时间',fontproperties='SimHei',fontsize=15,color='green')
plt.ylabel('纵轴：振幅',fontproperties='SimHei',fontsize=15)
plt.title('正弦波实例$y=cos(2\pi x)$',fontproperties='SimHei',fontsize=25)
plt.annotate('$\mu=100$',xy=(2,1),xytext=(3,1.5),arrowprops=dict(facecolor='black',shrink=0.1,width=2))

plt.axis([-1,6,-2,2])
plt.grid(True)
plt.show()