Thursday, December 21, 2017

calculus - Indeterminate form 00 using L'hospitals rule when calculating limxto0+xsin(x)


Given the question limx0+xsin(x)



I have deducted so far that this has the indeterminate form 00 so I have taken the natural logarithm of both sides to give me: limx0+ln(y)=limx0+sin(x)ln(x) This still has an indeterminate form so I rearrange it to start using L'hospitals rule: limx0+ln(x)csc(x) =limx0+1xcsc(x)cot(x) =limx0+sin(x)tan(x)x =limx0+cos(x)sec2(x)1=1 limx0+xsin(x)=1e


I don't think this is correct, am I doing something wrong, and if so, where?


Answer




limx0+xsin(x)



=limx0+exp(ln(x)sin(x))


=exp(limx0+ln(x)sin(x))


=exp(limx0+ln(x)1/sin(x))


Applying L'Hôpital's rule:



=exp(limx0+sin(x)2xcos(x))


=exp(1limx0+1cos(x)limx0+sin(x)2x)


=exp(limx0+sin(x)2x)


Applying L'Hôpital's rule:


=exp(limx0+2cos(x)sin(x))


e0=1


=1


No comments:

Post a Comment

analysis - Injection, making bijection

I have injection f:AB and I want to get bijection. Can I just resting codomain to f(A)? I know that every function i...