Calculating the Limit of a Complex Expression

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Homework Help Overview

The discussion revolves around calculating the limit of a complex expression involving a combination of trigonometric, logarithmic, and inverse trigonometric functions as \( x \) approaches 0.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the use of l'Hôpital's rule, with one expressing difficulty due to the emergence of a "weird function." Another participant suggests that certain factors can be set aside if they approach a nonzero finite limit.

Discussion Status

Some participants are actively working through the application of l'Hôpital's rule and sharing their findings. There is a recognition of the limits approaching positive and negative infinity, indicating a complex behavior of the limit as \( x \) approaches 0.

Contextual Notes

There is an emphasis on the behavior of the logarithmic function and the arcsine function as \( x \) approaches 0, with participants questioning the implications of these behaviors on the limit calculation.

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Homework Statement



\lim_{x \rightarrow 0} \frac{(1+tan(3x))^{1/3} x^2}{log_2(arcsin(x^3)+1)}

Homework Equations





The Attempt at a Solution



i tried to use l'hopital twice but i get a very weird function, so there another way to calculate it?
 
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blob84 said:

Homework Statement



\lim_{x \rightarrow 0} \frac{(1+tan(3x))^{1/3} x^2}{log_2(arcsin(x^3)+1)}

Homework Equations


The Attempt at a Solution



i tried to use l'hopital twice but i get a very weird function, so there another way to calculate it?

I'd be interested to see these weird functions. l'Hopital is the best way to do it. There is a trick that might help you. lim x->0 (1+tan(3x))^(1/3)=1. That's pretty harmless. I wouldn't include it in the l'Hopital treatment. In general if a factor of your function has a nonzero finite limit, just set it aside and concentrate on the rest.
 
thank you Dick,
i get:
Dx^2= 2x,
D log_{2}(arcsin(x^3)+1)=\frac{3x^2}{log2(arcsin(x^3)+1)\sqrt{1-x^6}},
\lim_{x \to 0} \frac{2x}{\frac{3x^2}{log{2} (arcsin(x^3)+1) \sqrt{1-x^6} } } = <br /> \frac{2}{3}\lim_{x \to 0} \frac{log{2} (arcsin(x^3)+1) \sqrt{1-x^6}} {x} →<br /> \frac{2}{3}\lim_{x \to 0^-} \frac{log{2} (arcsin(x^3)+1) \sqrt{1-x^6}} {x}= \frac{log2}{0^-} = -\infty \vee<br /> \frac{2}{3}\lim_{x \to 0^+} \frac{log{2} (arcsin(x^3)+1) \sqrt{1-x^6}} {x} = \frac{log2}{0^+}=+\infty<br />
 
blob84 said:
thank you Dick,
i get:
Dx^2= 2x,
D log_{2}(arcsin(x^3)+1)=\frac{3x^2}{log2(arcsin(x^3)+1)\sqrt{1-x^6}},
\lim_{x \to 0} \frac{2x}{\frac{3x^2}{log{2} (arcsin(x^3)+1) \sqrt{1-x^6} } } = <br /> \frac{2}{3}\lim_{x \to 0} \frac{log{2} (arcsin(x^3)+1) \sqrt{1-x^6}} {x} →<br /> \frac{2}{3}\lim_{x \to 0^-} \frac{log{2} (arcsin(x^3)+1) \sqrt{1-x^6}} {x}= \frac{log2}{0^-} = -\infty \vee<br /> \frac{2}{3}\lim_{x \to 0^+} \frac{log{2} (arcsin(x^3)+1) \sqrt{1-x^6}} {x} = \frac{log2}{0^+}=+\infty<br />

Looks ok to me!
 

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