Posted by Ifi on .
dx/dy cos x sin y + x^5 = 11
i got dx/dy= (cos x cos y)/ (sin x sin y +5x^4)
But the wolfram got
(1 cos x cos y)/(5x^4sin y sin x), where is the 1 come from?

Math 
Reiny,
so we are differentiating
cosx siny + x^5 = 11 implicitly ?
cosx(cosy) dy/dx + siny(sinx) + 5x^4 = 0
dy/dx = (sinx siny  5x^3)/(cosx cosy)
which agrees with my Wolfram result
http://www.wolframalpha.com/input/?i=find+dy%2Fdx+for+%28cos%28x%29%29%28sin%28y%29%29+%2B+x%5E5+%3D+11 
Math 
Reiny,
just noticed you wanted dx/dy (strange)
cosx siny + x^5 = 11
cosx(cosy) + siny(sinx) dx/dy = 5x^4 dx/dy = 0
dx/dy (5x4  sinxsiny) =  cosxcosy
dx/dy = cosxcosy/(5x^4  sinxsiny)
the same as yours. 
Math 
Ifi,
At reiny .... Thanks