diff --git a/docs/chapter2/chapter2.md b/docs/chapter2/chapter2.md
index 33f640a..3ef1156 100644
--- a/docs/chapter2/chapter2.md
+++ b/docs/chapter2/chapter2.md
@@ -162,7 +162,7 @@ $$
 
 > Law of total expectation 也被称为 law of iterated expectations(LIE)。如果 $A_i$ 是样本空间的有限或可数的划分(partition)，则全期望公式可以写成如下形式：
 > $$
-> \mathrm{E}(X)=\sum_{i} \mathrm{E}\left(X \mid A_{i}\right) \mathrm{P}\left(A_{i}\right) \nonumber
+> \mathrm{E}(X)=\sum_{i} \mathrm{E}\left(X \mid A_{i}\right) \mathrm{P}\left(A_{i}\right)
 > $$
 
 **证明：**