f(x) = ax^2 + bx +c

tangent = (_2at + b)*(x-t)+at^2 +bt + c

normal = -_1/(_2at+b)*(x-t)+at^2 +bt + c

f(x) = sin(x)

tangent = cos(t)*(x-t)+sin(t)

normal = -sec(t)*(x-t)+sin(t)


y = a*exp(-(b/x)^n)+d

y = a*exp(-b*(x-c)^2)+d