Thank you for your quick reply. But I mean why do I have to define "c" in my last program 2 times? In worksheet and in program? Without it I can not get the right result. I think it would be right to define "c" one time in worksheet, isn't it?
So, is this thread is a bug report, or not? It would be great to correct this bug
For simple understanding:
Form MC help:
Local variables or functions defined with this operator may be assigned to values from the worksheet. For example, it's possible to define a:=2 in your worksheet, then define a local variable b ← a inside a program.
Mathcad 15.0 (M010 [MC15_M010_20110622])
PS: Does this bug manifests in other versions of MC? I do not know, because I've just begin to use MathCAD.