# Talk:Control-Lyapunov function

WikiProject Systems (Rated Start-class, Low-importance)
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## ${\displaystyle f(x)}$ or ${\displaystyle f(x,u)}$?
At the start of the article, ${\displaystyle f}$ is function of the single variable ${\displaystyle x}$. And at the end is dependent of ${\displaystyle u}$ also. I think that the article should be changed to avoid this. To solve it I suppose that first equation can be changed to read:
${\displaystyle {\dot {x}}(t)=f(x(t),\,u(t)),}$
## Positive definiteness of ${\displaystyle V(x,u)}$
It should be made clear if positive definiteness of ${\displaystyle V}$ is withs respect to ${\displaystyle x}$ or both ${\displaystyle x}$ and ${\displaystyle u}$. I would say for the explanation that is only for ${\displaystyle x}$, but I feel that something is missing in the explanation. —Preceding unsigned comment added by 132.206.73.6 (talk) 01:56, 20 May 2010 (UTC)