diff --git a/geom/math.py b/geom/math.py
index 417ce9f..3734360 100644
--- a/geom/math.py
+++ b/geom/math.py
@@ -62,4 +62,4 @@ def is_equal(x1, y1, x2, y2):
     """Returns true if two unit vectors are pointed in either the same or
     opposite directions.
     """
-    return math.isclose(abs(dot(x1, y1, x2, y2)), 1, rel_tol=1e-03)
+    return math.isclose(abs(dot(x1, y1, x2, y2)), 1, rel_tol=1e-05)