diff --git a/HP48_notes.txt b/HP48_notes.txt
index 72d8892..c760415 100644
--- a/HP48_notes.txt
+++ b/HP48_notes.txt
@@ -1,7 +1,7 @@
 
 
 To get an HP48 ploting the frequerncy response of a 
-Z transform, first define Z as 'EXP(-(0,1)).
+Z transform, first define Z as 'EXP(X*(0,-1)).
 
 i.e.