wedge product of $0$ and $dx$ I am learning differential form and I have a question about $\land$ How do we calculate $0 \land dx$? is it equal $0$? If it is, why?

The wedge product of a function and a one-form is just multiplication by the function. Since the function here is zero, you just get zero.

Explicitly, if $f$ is a function and $\omega$ is a one-form, then $(f\wedge \omega)_p=f(p)\omega_p.$ In this case, $f=0,$ so for any $p$, $f(p)=0.$