diff --git a/docs/02 Lighting/05 Light casters.md b/docs/02 Lighting/05 Light casters.md
index 696eab4..63eb6cd 100644
--- a/docs/02 Lighting/05 Light casters.md	
+++ b/docs/02 Lighting/05 Light casters.md	
@@ -286,7 +286,7 @@ $$
 0.97|14|0.91|25|0.82|35|0.91 - 0.82 = 0.09|0.97 - 0.82 / 0.09 = 1.67
 0.83|34|0.91|25|0.82|35|0.91 - 0.82 = 0.09|0.83 - 0.82 / 0.09 = 0.11
 0.64|50|0.91|25|0.82|35|0.91 - 0.82 = 0.09|0.64 - 0.82 / 0.09 = -2.0
-0.966|15|0.9978|12.5|0.953|17.5|0.966 - 0.953 = 0.0448|0.966 - 0.953 / 0.0448 = 0.29
+0.966|15|0.9978|12.5|0.953|17.5|0.9978 - 0.953 = 0.0448|0.966 - 0.953 / 0.0448 = 0.29
 
 你可以看到，我们基本是在内外余弦值之间根据\(\theta\)插值。如果你仍不明白发生了什么，不必担心，只需要记住这个公式就好了，在你更聪明的时候再回来看看。