I have drawn a circle by doing this in Matlab: syms x; ezplot(cos(x),sin(x))
I get the tangent point at which I want my tangent to be by taking $x = \cos(3.1415)$, $y = \sin(3.1415)$, but now I am confused because normally I would differentiate the function to get the slope.
Now I have two functions that created my curve, which one do I differentiate to get the slope?