Update cake_eating_problem.md

Author: nisha617

lectures/cake_eating_problem.md

@@ -38,6 +38,10 @@ kernelspec:
 
 ```{code-cell} ipython
 import matplotlib.pyplot as plt
+FONTPATH = "fonts/SourceHanSerifSC-SemiBold.otf"
+mpl.font_manager.fontManager.addfont(FONTPATH)
+plt.rcParams['font.family'] = ['Source Han Serif SC']
+
 import numpy as np
 ```
 ## 模型