相关的文档：

• Annotating axis

• annotate() command

http://i.imgur.com/KOKKzbl.pngMatplotlib】 在绘图中标注点的方法" TITLE="【Python Matplotlib】 在绘图中标注点的方法" />

标注的代码如下：

...

t = 2 * np.pi / 3
plt.plot([t, t], [0, np.cos(t)], color='blue', linewidth=2.5, linestyle="--")
plt.scatter([t, ], [np.cos(t), ], 50, color='blue')

plt.annotate(r'$sin(\frac{2\pi}{3})=\frac{\sqrt{3}}{2}$',
 xy=(t, np.sin(t)), xycoords='data',
 xytext=(+10, +30), textcoords='offset points', fontsize=16,
 arrowprops=dict(arrowstyle="->", connectionstyle="arc3,rad=.2"))

plt.plot([t, t],[0, np.sin(t)], color='red', linewidth=2.5, linestyle="--")
plt.scatter([t, ],[np.sin(t), ], 50, color='red')

plt.annotate(r'$cos(\frac{2\pi}{3})=-\frac{1}{2}$',
 xy=(t, np.cos(t)), xycoords='data',
 xytext=(-90, -50), textcoords='offset points', fontsize=16,
 arrowprops=dict(arrowstyle="->", connectionstyle="arc3,rad=.2"))
...