Re: Turning Derivative into Function (Newbie Question)

*To*: mathgroup at smc.vnet.net*Subject*: [mg115481] Re: Turning Derivative into Function (Newbie Question)*From*: dsnead6 at charter.net*Date*: Wed, 12 Jan 2011 04:07:02 -0500 (EST)

Define g as g[x_]:=f'[x] --Dave On Tue, Jan 11, 2011 at 3:58 AM, Just A Stranger wrote: > When I apply a function that outputs another function, how come I can > not > pass arguments to the new function? Am I missing some principle about > how > Mathematica functions work? Could someone please point me to the > relevant > documentation? > > > A simple example to illustrate my confusion: > > In[1]: f[x_] := x^2 > In[2]: g := f'[x] > > So now I have: > > In[3]: g > out[3]: 2x > > as expected > > So how come I get the following when trying to pass an argument to g: > > In[4]: g[2] > Out[4]: 2x[2] > > Instead of the output I want: > > *Ou[4]: 4 > > > I tried > > In: g[x_] := f'[x] > > But it seems to think I'm trying to assign a function to Times. > "SetDelayed::write: Tag Times in (2 x)[y_] is Protected. >>" > > Thank you very much for any help :)