Prove: If and are functions and then .
Now I know that this is a personal peeve of mine.
I give Charles Pinter full credit for making me aware of this problem.
It is a notational problem.
Suppose that and what sense does it make to write
I agree with him, it makes no sense. But I disagree with his notation.
He uses for .
And if then is used for .
I suggested the more intuitive notations but never got any real takers.