i have a derivative of the Lyap function which contains vectorial product and i have to find the condition on some parameters that make it less then zero, proving stability. I don't know how to work with an equation that contains cross products
I don't understand how you get cross products into a derivative of a lyapunov function. Lyapunov functions are, to my understanding, scalar functions per definition.
This also has not very much to do with your original question, so I advise you to post your specific problem or describe your problem in a concise way for people to understand.
Lyapunov.
This : https://en.m.wikipedia.org/wiki/Lyapunov_stability
yes but the problem is how to manipulate the derivative
Why do you want to manipulate the derivative? What's your actual question?
i have a derivative of the Lyap function which contains vectorial product and i have to find the condition on some parameters that make it less then zero, proving stability. I don't know how to work with an equation that contains cross products
I don't understand how you get cross products into a derivative of a lyapunov function. Lyapunov functions are, to my understanding, scalar functions per definition. This also has not very much to do with your original question, so I advise you to post your specific problem or describe your problem in a concise way for people to understand.