Use direction_to, remove code example for manually normalizing (#3330)

Also link to matrices and transforms and 3Blue1Brown from within the advanced vector math article.

tutorials/math/vector_math.rst

@@ -188,25 +188,8 @@ Normalization
 
 **Normalizing** a vector means reducing its length to ``1`` while
 preserving its direction. This is done by dividing each of its components
-by its magnitude:
-
-.. tabs::
- .. code-tab:: gdscript GDScript
-
-    var a = Vector2(2, 4)
-    var m = sqrt(a.x*a.x + a.y*a.y)  # get magnitude "m" using the Pythagorean theorem
-    a.x /= m
-    a.y /= m
-
- .. code-tab:: csharp
-
-    var a = new Vector2(2, 4);
-    var m = Mathf.Sqrt(a.x*a.x + a.y*a.y);  // get magnitude "m" using the Pythagorean theorem
-    a.x /= m;
-    a.y /= m;
-
-Because this is such a common operation, ``Vector2`` and ``Vector3`` provide
-a method for normalizing:
+by its magnitude. Because this is such a common operation,
+``Vector2`` and ``Vector3`` provide a method for normalizing:
 
 .. tabs::
  .. code-tab:: gdscript GDScript
@@ -291,12 +274,12 @@ the order of the two vectors does not matter:
  .. code-tab:: gdscript GDScript
 
     var c = a.dot(b)
-    var d = b.dot(a)  # these are equivalent
+    var d = b.dot(a) # These are equivalent.
 
  .. code-tab:: csharp
 
     float c = a.Dot(b);
-    float d = b.Dot(a);  // these are equivalent
+    float d = b.Dot(a); // These are equivalent.
 
 The dot product is most useful when used with unit vectors, making the
 first formula reduce to just ``cosθ``. This means we can use the dot
@@ -319,7 +302,8 @@ zombies ``A`` and ``B``. Assuming a zombie's field of view is **180°**, can the
 The green arrows ``fA`` and ``fB`` are **unit vectors** representing the
 zombies' facing directions and the blue semicircle represents its field of
 view. For zombie ``A``, we find the direction vector ``AP`` pointing to
-the player using ``P - A`` and normalize it. If the angle between this
+the player using ``P - A`` and normalize it, however, Godot has a helper
+method to do this called ``direction_to``. If the angle between this
 vector and the facing vector is less than 90°, then the zombie can see
 the player.
 
@@ -328,13 +312,13 @@ In code it would look like this:
 .. tabs::
  .. code-tab:: gdscript GDScript
 
-    var AP = (P - A).normalized()
+    var AP = A.direction_to(P)
     if AP.dot(fA) > 0:
         print("A sees P!")
 
  .. code-tab:: csharp
 
-    var AP = (P - A).Normalized();
+    var AP = A.DirectionTo(P);
     if (AP.Dot(fA) > 0)
     {
         GD.Print("A sees P!");

tutorials/math/vectors_advanced.rst

@@ -586,3 +586,14 @@ So the final algorithm is something like:
     {
         GD.Print("Polygons Collided!");
     }
+
+More information
+~~~~~~~~~~~~~~~~
+
+For more information on using vector math in Godot, see the following article:
+
+- :ref:`doc_matrices_and_transforms`
+
+If you would like additional explanation, you should check out
+3Blue1Brown's excellent video series "Essence of Linear Algebra":
+https://www.youtube.com/watch?v=fNk_zzaMoSs&list=PLZHQObOWTQDPD3MizzM2xVFitgF8hE_ab