September 9th, 2010, 03:02 PM  #1 
Member Joined: Sep 2010 Posts: 32 Thanks: 0  ISSUES with circles...
A circle in R^3, ie 3D space is written as: f(x,y)= x^2+ y^2 If we want to draw level curves we give the function different values of C, for example: C= 1 > x^2+ y^2 = 1, This will give us a circle with the center in (0,0) and the radius = sqrt(1)=1 BUT what changes when we have x^2+ 4y^2 What does the 4 change, does it change the centre of the circle? Also, how should one sketch x^2+y^2+z^2 < 5?? An answe to any of the two questions is highly appreciated... Please help me! 
September 9th, 2010, 03:21 PM  #2  
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,968 Thanks: 1152 Math Focus: Elementary mathematics and beyond  Re: ISSUES with circles... Quote:
 
September 10th, 2010, 01:29 PM  #3  
Member Joined: Aug 2010 Posts: 49 Thanks: 0  Re: ISSUES with circles... Quote:
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You seem to misunderstand functions. Think about what R^n > R^m means, as a hint.  
September 10th, 2010, 05:43 PM  #4 
Member Joined: Sep 2010 Posts: 32 Thanks: 0  Re: ISSUES with circles...
ok good point but is it not possible to draw level curves for f(x,y)= x^2+ y^2 by assigning it different constants? 
September 11th, 2010, 02:42 AM  #5  
Global Moderator Joined: Oct 2008 From: London, Ontario, Canada  The Forest City Posts: 7,968 Thanks: 1152 Math Focus: Elementary mathematics and beyond  Re: ISSUES with circles... Quote:
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September 11th, 2010, 08:00 AM  #6 
Member Joined: Sep 2010 Posts: 32 Thanks: 0  Re: ISSUES with circles...
Thank you very much greg1313, that cleared up a lot!


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