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Mathematics 18 Online
OpenStudy (anonymous):

Another limit question...

OpenStudy (anonymous):

\[\lim_{n \rightarrow \infty}\ln\left( 1+ \frac{ 4-\sin(x) }{ n } \right)^n\]

OpenStudy (anonymous):

My approach was that I raised it to the power of e and then I Just found the limit of the stuff inside. But that's as far as I got.... I see a pattern of (1+(1/x))^n which is the definition of e but I don't really know about this one...

hartnn (hartnn):

4 -sin x or 4 - sin n ?? if its 4- sin x, then its a constant...

OpenStudy (anonymous):

Nope that is not a typo. It is indeed a constant.

hartnn (hartnn):

cool! so you have the function of the form \((1+ax)^{1/x}\) right?

OpenStudy (anonymous):

How so?

OpenStudy (anonymous):

Okay well I can see it if you make a substitution.

OpenStudy (anonymous):

Go on.

hartnn (hartnn):

good, i'll tell you what we do in case of \((1+ax)^{1/x}\) -- > \((1+ax)^{1/x} = [(1+ax)^{\frac{1}{ax}}]^a\) and then use the limit formula, (if you can use) \(\lim \limits_{x\to \infty} (1+1/x)^x = e\)

OpenStudy (anonymous):

Brilliant! But the limit would then be 1 not 0...

OpenStudy (anonymous):

Which according to wolfram it's 0.

OpenStudy (anonymous):

Ohh wait. I goofed. Have to take the ln of that.

OpenStudy (anonymous):

ln(1) is 0. Thank you!

hartnn (hartnn):

in the wolf, its shows ln^n

OpenStudy (anonymous):

Yeah it's a notational thing. That just the inside raised to the n.

OpenStudy (anonymous):

Kinda like sin^2(x) and (sin(x))^2.

hartnn (hartnn):

okk... i thought the answer would be 4- sin x ..

OpenStudy (anonymous):

Nah. It's 0.

hartnn (hartnn):

:)

OpenStudy (anonymous):

@hartnn : So I got up here.

OpenStudy (anonymous):

\[\lim_{b \rightarrow 0}(1+(4-\sin(x)b)^{\frac{ 1 }{ b }}\]

OpenStudy (anonymous):

Is that okay so far or am I way off?

hartnn (hartnn):

i assume there is ln outside of that limit and you just plugged in b =1/n

OpenStudy (anonymous):

Indeed sir.

hartnn (hartnn):

yes, go on

OpenStudy (anonymous):

Stuck >.< .

OpenStudy (anonymous):

Like I know that should be e but I'm having trouble relating it to the definition.

hartnn (hartnn):

whatever expression is with \(\Large 1+ ...\) that same expression should be with \(\Large \dfrac{1}{...}\) thats how I remember so we have 1+ (4-sin x)b so the fraction in the exponent should be \(\Large \dfrac{1}{(4-\sin x)b}\)

hartnn (hartnn):

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