define a function with variable coefficients
- To: mathgroup at smc.vnet.net
- Subject: [mg105861] define a function with variable coefficients
- From: Andong He <he at math.psu.edu>
- Date: Tue, 22 Dec 2009 04:04:56 -0500 (EST)
Hi,
I wanna define f[z_, t_] = Sum[a_j*z^j, {j, 1, n}], where I use "_j" and "^j" to denote the subscript and superscript. It gives a f as a series, which is fine.
But if I want a_j to be functions of t, say
f[z_, t_] = Sum[a_j[t]*z^j, {j, 1, n}],
it yields something which doesn't make sense. For example, it has terms a_(1+n)[t] and a_(2+n)[t] which are not even defined in my expression for f!!!
Can anyone help me figure out what's going on? Thanks!