If You have a function implicity defined as...
(1)
... its derivative in a point is...
(2)
In Your case is , , , so that is . A more simple solution for this particular case is to write (1) as so that . The 'right' passes from the point so that is and ...
Kind regards
I've manged to get the answer 1.
But that was only a lucky guess steming from the research I did on this website.
http://www.math.ucdavis.edu/~kouba/CalcOneDIRECTORY/implicitdiffdirectory/ImplicitDiff.html