November 28th, 2010, 03:35 AM  #1 
Senior Member Joined: Oct 2009 Posts: 895 Thanks: 1  Questions in derivatives
Hi all what is the derivative of ysin(1/y)=1xy my answr derivative (ysin(1/y)= derivative (1xy) y.cos(1/y).(y^2) + sind(1/y).y' = xy'y y'(y/ycos(1/y).(y^2)+x)  find dr/dQ cosr + cosQ=rQ my answar derivative(cosr ) + derivative( cosQ) = derivative (rQ) sinr + cosQ = r+sinQ plese (correcrt to me and explaine whre I do mistake ) 
November 28th, 2010, 05:55 AM  #2 
Senior Member Joined: Nov 2010 From: Staten Island, NY Posts: 152 Thanks: 0  Re: Questions in derivatives
Corrections are in bold: y.cos(1/y).(y^2)y' + sin(1/y).y' = xy'y (sinr)r' sin Q= r+Qr' 
November 28th, 2010, 06:49 AM  #3 
Senior Member Joined: Oct 2009 Posts: 895 Thanks: 1  Re: Questions in derivatives
in question 1 why you put y' after cos(1/y).(y^2) ? 
November 28th, 2010, 11:31 AM  #4 
Senior Member Joined: Nov 2010 From: Staten Island, NY Posts: 152 Thanks: 0  Re: Questions in derivatives
If y=f(x), then when differentiating implicitly, you always follow a derivative involving y by dy/dx. This is due to the chain rule. For example, the derivative of is 

Tags 
derivatives, questions 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Are partial derivatives the same as implicit derivatives?  johngalt47  Calculus  2  November 23rd, 2013 11:44 AM 
2 questions (limits/derivatives)  jkh1919  Calculus  9  October 6th, 2012 03:21 PM 
Questions in derivatives  rsoy  Calculus  3  November 4th, 2010 02:42 PM 
Questions in derivatives  rsoy  Calculus  2  November 3rd, 2010 10:31 PM 
Questions in derivatives  rsoy  Calculus  2  November 3rd, 2010 09:25 PM 