Implicit Differentiation
implicit differentiation can be complicated and counter-intuitive<p>for example:<p>9=y^2+x^2 find y&#x27; the answer is NOT 2y<p>so if you jsut studied calculus, this new rule invalidates what you just learned<p>I hardly use it even though I  do use calculus in some of my work.  Usually I just need to get the differential of a single variable of a function of the form w=f(x,y,z) or such. I think implicit notation makes things more confusing.