I'm trying to use $f'(x)$ in a ecuation wear it need to be converted to be used sort like $cos(g(f'(x)))$ whear $g(x) = y$ rad or deg
What I'm currently working on is to get this ecuation to work with horizontal lines. $$f (x) ^ 2 + x ^ 2 ) ^ .5 ( f (x) / ( f (x) ^ 2 + x ^ 2 ) ^ .5 = y$$ And that is is the same as $f(x)=y$