How can I define function with another function?

Questions
1

Hi, I’m trying to learn using Mathematica and I can’t figure out, how to insert a function into another function definition.

Ampl[t_]:=A*Exp[Alpha*t]
Equation[t_]:=-5*Exp[-4*Ampl[t]]+3*Ampl[t]-4*Ampl[t]^2+2

The result is

"Tag Plus is Protected."

I found some examples of this error like

http://superuser.com/questions/340289/setwrite-tag-plus-in-something-is-protected

But I can’t see, how this is related, because I don’t try to give a new definition to a protected symbol.

Sorry for a dumb question, but I’m used to work in Maple and it works there with no problem. Thanks for any advice.

2

On my system it works fine. The error message is probably from a conflict between your current assignement for Ampl and Equation and some other assignments that you gave earlier in the session and that is still in memory. Try with
Clear[Ampl,Equation]; Ampl[t_] := A*Exp[Alpha*t] Equation[t_] := -5*Exp[-4*Ampl[t]] + 3*Ampl[t] - 4*Ampl[t]^2 + 2

3

It works now. Thank you very much. I didn’t think of that.