some time ago I was faced with a problem: I need to find the Taylor expansion with polynomial degree 3 for those two functions: $$ f(x,y,z) = y^3\cos(xz^2) \\\text{and} \\ \\ f(x,y,z,w) = x^2yz+xyw^4. $$ How can I do this? I know the general formula for 2 variables with degree 3, but I have no idea when we have 3 or 4 of them.
In this link, there are some answers but I cant understand where to stop (they don't especificate the degree of polynomial).
Thanks in advance!
