change symbolic variable by another

[thefantasticme]

Hi

i would like to know if there is any function that can be used to change a symbolic variable with another one (i.e: a polynomial expression is function of time, “t”, and as I need to make a convolution I would like to change it, lets say by tau, “tau”).

gabi

 

[thefantasticme]

i finally found the function: "subs"
olé!!!!!