Saturday, 7 November 2015

calculus - Limit of a function



I'm struggling with this limit :



limx0(xcotx)1x2



It's in the 00 form, so I tried to use L'Hospital's rule:
limx0((xcotx)1)(x2)=limx0cotxxcsc2x2x=10100

I'm not sure how to continue. I tried to derivate more, but only got similar expressions or 00. The result should be 13, so guess I'm doing something wrong. I would appreciate if somebody could tell me how to solve this one.



Thanks for help.


Answer



xcotx1x2=xcosxsinxx3xsinx=(xsinxx3+cosx1x2)xsinx
hence the limit of the RHS as x0 is 1612=13.


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