diff --git a/code/mymath.py b/code/mymath.py
index 2cf42cf..7e67bec 100644
--- a/code/mymath.py
+++ b/code/mymath.py
@@ -8,7 +8,7 @@ def sinc2d(x,y):
     elif y==0:
         return m.sin(x)/x
     else:
-        return (m.sin(x)/x)*(m.sin(y)/y)
+        return (m.cos(x-y) - m.cos(x+y))/(2*x*y)
     
 def addone(x):
     return x+1