FindRoot problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg40032] FindRoot problem*From*: "Pigeon, Robert" <Robert.Pigeon at drdc-rddc.gc.ca>*Date*: Sun, 16 Mar 2003 02:48:07 -0500 (EST)*Sender*: owner-wri-mathgroup at wolfram.com

Good day, I have a problem with FindRoot that I do not understand, so I am asking for help! I have a function defined as a Module. I use FindRoot to find a root when the function is given a value. Everything works fine except when I put a condition to my function, when I do I get an error message. Here what I try to do: f[x_]:= Module[{}, Sec[x] - 0.0018167 (Sec[x]-1) - 0.002875 (Sec[x]-1)^2 - 0.000808 (Sec[x]-1)^3 ]; f::usage="explanation of f"; If I do FindRoot[f[x]==10,{x,1.4}] I get {x->1.53501} All that is correct. But now if I do f[x_ /; x>= 0 && x<= 1.54]:= same as above and I try to find the root the same way, I get an error message FindRoot[f[x]==10,{x,1.4}] I get FindRoot::frjc: Could not symbolically find the Jacobian of {f[x]-10. Try giving two starting values for each variable. I tried putting my conditions inside the Module, after the Module. I tried to use Which, If. But, as soon as I put a condition, I get the same error. Any idea ??? Thanks, Robert

**Follow-Ups**:**Re: FindRoot problem***From:*Dr Bob <drbob@bigfoot.com>