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December 3rd, 2015, 03:11 PM  #1 
Newbie Joined: Dec 2015 From: Nj Posts: 3 Thanks: 0  Separation of variables
I am not sure whether I did this correctly. If the separation of variables method doesn't work, I can use the exact method. Please confirm or help me on my problem, thank you!! Last edited by skipjack; December 9th, 2015 at 06:08 AM. 
December 3rd, 2015, 04:09 PM  #2 
Math Team Joined: May 2013 From: The Astral plane Posts: 1,797 Thanks: 715 Math Focus: Wibbly wobbly timeywimey stuff. 
It looks good but for one thing: $\displaystyle \int \frac{du}{u} = \ln  u  $. Dan Last edited by skipjack; December 5th, 2015 at 02:03 AM. Reason: Rewrite 
December 3rd, 2015, 04:14 PM  #3 
Math Team Joined: Dec 2013 From: Colombia Posts: 7,313 Thanks: 2447 Math Focus: Mainly analysis and algebra 
I see more problems with the question than with your solution. I think you forgot to cross out a $y$ in line 2.

December 4th, 2015, 08:55 AM  #4 
Math Team Joined: Jan 2015 From: Alabama Posts: 3,199 Thanks: 873 
Your original equation is given as $\displaystyle \frac{dy}{dx}= (x^2+ 1)(\tan(y))y'x$. What does the y' mean on the right? Last edited by skipjack; December 5th, 2015 at 02:04 AM. 
December 6th, 2015, 07:41 AM  #5 
Newbie Joined: Dec 2015 From: Nj Posts: 3 Thanks: 0 
I have the same problem with the question as well. I felt as if the problem was written incorrectly, but my professor assured me it's fine. The y' is y prime? I honestly think the problem is just messed up and I really don't want to lose any points on this one :/ If anyone sees this and can confirm my question/answer that would be awesome.
Last edited by skipjack; December 9th, 2015 at 06:02 AM. 
December 6th, 2015, 07:44 AM  #6 
Newbie Joined: Dec 2015 From: Nj Posts: 3 Thanks: 0  
December 9th, 2015, 05:43 AM  #7  
Math Team Joined: Jan 2015 From: Alabama Posts: 3,199 Thanks: 873  Quote:
Last edited by skipjack; December 9th, 2015 at 06:04 AM.  
December 9th, 2015, 06:20 AM  #8 
Global Moderator Joined: Dec 2006 Posts: 19,066 Thanks: 1622  The equation appears to end with $y'\!x\!$, but that doesn't appear in your work. Sometimes, $y'$ is used to mean $\dfrac{dy}{dx}$, but that wouldn't make sense here. Perhaps $y'\!x$ was intended to be $y/x$. Was anyone else also given this problem, but given some other explanation?


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separation, seperation, variables 
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