diff --git a/题库0.3/BasicKnowledge.json b/题库0.3/BasicKnowledge.json
index ead20e3a..52ebc4ba 100644
--- a/题库0.3/BasicKnowledge.json
+++ b/题库0.3/BasicKnowledge.json
@@ -1511,7 +1511,7 @@
             "K0508002B",
             "K0508003B"
         ],
-        "content": "向量夹角的坐标表示: $\\cos \\langle\\overrightarrow{a}, \\overrightarrow{b}\\rangle=\\dfrac{\\overrightarrow{a}\\cdot \\overrightarrow{b}}{|\\overrightarrow{a}||\\overrightarrow{b}|}=\\dfrac{x_1 x_2+y_1 y_2}{\\sqrt{x_1^2+y_1^2}\\cdot \\sqrt{x_2^2+y_2^2}}$\\."
+        "content": "向量夹角的坐标表示: $\\cos \\langle\\overrightarrow{a}, \\overrightarrow{b}\\rangle=\\dfrac{\\overrightarrow{a}\\cdot \\overrightarrow{b}}{|\\overrightarrow{a}||\\overrightarrow{b}|}=\\dfrac{x_1 x_2+y_1 y_2}{\\sqrt{x_1^2+y_1^2}\\cdot \\sqrt{x_2^2+y_2^2}}$."
     },
     "B00210": {
         "lesson": "K0508",