diff --git a/maths/arc_length.py b/maths/arc_length.py
index 9e87ca38c..94d5f440e 100644
--- a/maths/arc_length.py
+++ b/maths/arc_length.py
@@ -12,4 +12,4 @@ def arc_length(angle: int, radius: int) -> float:
 
 
 if __name__ == "__main__":
-    print(arc_length(90, 10))
+    print(arc_length(90, 10)) # --> 15.7079632679