Posted by Molly on .
Find dy/dx by implicit differentiation.
x cos y + y cos x = 1

calculus 
Steve,
just use the product rule and go for it:
cosy  x siny y' + y' cosx  y sinx = 0
y'(cosx  x siny) = y sinx  cosy
y' = (y sinx  cosy) / (cosx  x siny)