I guess then the question is "what is F". That is, what does the function F represent in that formula? Are the subscripts indices or derivatives? And if they are derivatives, what do F' and F'' mean?
Ok, so, i have a serious problem and i need help, since english is not my mother language i'm not sure if this is the right name of the problem..
i have function in implicit shape y^2 = x^2 * ((4+x)/(4-x))
and for the curvature there is formula
and i don't understand how to get to those parameters