Simple question in Mathematica: find value of function

[Sosi]

Hi guys!

I'm trying to the value of x when a function F[x] has a certain expression. I'm computing the value of F[x] using NDSolve and a set of differential equations - all numerically. Yet, I can't find an easy and systematic way to find the value of x when F[x]=constant.

I tried using NMinimize:

NMinimize[{Evaluate[CONSTANT- 
    F[x] /. systemofequations, x]

Yet, I can't seem to find a good way to compute the value of x.. :S

Do you guys have any suggestions on how I could try to solve this issue?
Thanks so much

 

[Sosi]

well, FindRoot was what I was looking for. Found it here:

https://www.physicsforums.com/showthread.php?t=375633

Sorry to have created a new thread, I only found the link above afterwards.