sorry for such basic question but I have problem with understanding partial derivative. I watched some videos about that, and read some articles, bo with no result.
As I understand partial derivative gives me functions which are tengent to my main (parent) function. In all tutorials that I've seen, they give example for $f(x,y)$. What you can write as $z = f(x,y)$
But I need tangent line to function of just one variable, like $f(x)$
So it seems to be obvious to just set $z=0$
So let's say my function is $f(x) = x^2$
I can write it as $y = x^2$
So after partial derivative on $x$, I get: $y=2x$
And it's definetaly not tangent to $y=x^2$
I see I make some logical error, but don't know where and how to fix it. Could anyone help me please? Great thanks in advance