RE: how can I solve a function Erfc
- To: mathgroup at smc.vnet.net
- Subject: [mg48428] RE: [mg48396] how can I solve a function Erfc
- From: "David Park" <djmp at earthlink.net>
- Date: Sat, 29 May 2004 03:06:50 -0400 (EDT)
- Sender: owner-wri-mathgroup at wolfram.com
Aude,
How about something like this...
f[L_][t_] := Erfc[L/(2000*Sqrt[2]*Sqrt[t])]
You can look for roots by plotting the function, adjusting the iterator
domain for various values of L.
Plot[f[2000][t], {t, 0, 200},
PlotRange -> {0.8, 1.0},
ImageSize -> 500];
You can find a specific root, say for L == 2000 with...
FindRoot[f[2000][t] == 0.9, {t, 1}]
{t -> 63.3281}
Writing a general function g to return t for a given L...
g[L_] := t /. FindRoot[f[L][t] == 0.9, {t, Sqrt[L]}]
You can then plot the solution...
Plot[g[L], {L, 0.01, 10^4},
ImageSize -> 500];
David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/
From: aude [mailto:montgermont.aude at ec-lille.fr]
To: mathgroup at smc.vnet.net
Hi,
I have to solve this function:
Erfc[L/(4*(Dg*t)^(1/2))]= 0.9
Dg is constant.
Dg=5*10^5
I want to plot t as a function of L.
thanks.
aude