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November 8th, 2009, 12:57 AM  #1 
Joined: Nov 2009 Posts: 1 Thanks: 0  Lim of sqrt (1cos(x)) / x when x> 0?
hi, i need to proof: lim sqrt (1cos(x)) / x when x>0. i think this limit is undefined, but i don't know how to prove it  without Le'Hopital's rule.. Thanks for your help! 
November 8th, 2009, 06:15 AM  #2 
Joined: Jun 2009 Posts: 150 Thanks: 0  Re: Lim of sqrt (1cos(x)) / x when x> 0?
Another approach would use the (first two nonzero terms of) the Maclaurin series for cos(x) .

November 8th, 2009, 05:45 PM  #3  
Global Moderator Joined: May 2007 Posts: 4,125 Thanks: 105  Re: Lim of sqrt (1cos(x)) / x when x> 0? Quote:
You end up with (sin(x)/x)/sqrt(1+cos(x)). You should have already sin(x)/x > 1 as x>0  

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