Hi, if I look at the solution set $M$ of the set of non-linear equations
$$\begin{cases} y_1&=x^2 \\ y_2&=x^3\end{cases}$$
this is a manifold. I can check this using the implicit function theorem by defining $f: \Bbb R^3 \to \Bbb R^2$ and
$$f(x,y_1,y_2) = \begin{bmatrix} y_1-x^2 \\ y_2-x^3\end{bmatrix}$$
and checking that the $2 \times 2$ matrix
$$\partial_{y_1,y_2}f = \begin{bmatrix} 1&0 \\ 0&1 \end{bmatrix}$$
is indeed non-singular. My question is if I don't use the suggestive notation $y_1,y_2$, but for example $y$ and $z$, how do I know which part of the total derivative of $f$ I …