Hello there,

I would like to do this:

let f(x) = 0.5*x^2 and plot it;
let g(x) = f'(x);
let h(x,y) = f(y) + g(y) * (x-y) and plot it;

This should plot the f function and its tangent line h in function of k, shouldn't it?
The problem is that I cannot define g as the derivative of f. Of course i don't need to plot it, i need its expression.

How can this be done?

Thanks a lot!!