From 6a781d0737c89e301ac2cc85557c73b0aa364fd8 Mon Sep 17 00:00:00 2001
From: Grant Sanderson <grant@3blue1brown.com>
Date: Thu, 23 Aug 2018 14:45:15 -0700
Subject: [PATCH] Bug fix to Arrow

---
 mobject/geometry.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mobject/geometry.py b/mobject/geometry.py
index cdc6bc7a..8dbb61a2 100644
--- a/mobject/geometry.py
+++ b/mobject/geometry.py
@@ -600,7 +600,7 @@ class Arrow(Line):
         return self
 
     def get_normal_vector(self):
-        p0, p1, p2 = self.tip[0].get_anchors()
+        p0, p1, p2 = self.tip[0].get_anchors()[:3]
         result = np.cross(p2 - p1, p1 - p0)
         norm = get_norm(result)
         if norm == 0: