A calculus problem by Parth Sankhe

Calculus Level 1

Evaluate lim x 0 + x x . \large \lim_{x\to0^+} x^x .

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1 solution

Jordan Cahn
Dec 10, 2018

As it turns out, it is not necessary to approach from the positive direction. We find first find ln lim x 0 x x = lim x 0 ln x x \ln \lim\limits_{x\to 0} x^x = \lim\limits_{x\to 0}\ln x^x . lim x 0 ln x x = lim x 0 x ln x = lim x 0 ln x 1 / x Apply L’H o ^ pital’s rule = lim x 0 1 / x 1 / x 2 = lim x 0 x = 0 \begin{aligned} \lim_{x\to 0} \ln x^x &= \lim_{x\to 0} x\ln x \\ &=\lim_{x\to 0} \frac{\ln x}{^1\!/\!_x} && \color{#3D99F6}\text{Apply L'H}\hat{\text{o}}\text{pital's rule}\\ &= \lim_{x\to 0} \frac{^1\!/\!_x}{-^1\!/\!_{x^2}} \\ &= \lim_{x\to 0} -x = 0 \end{aligned}

Thus, ln lim x 0 x x = 0 \ln \lim\limits_{x\to 0} x^x = 0 , so lim x 0 x x = 1 \lim\limits_{x\to 0} x^x = \boxed{1} .

This is a classic example of the limit-finding technique "it looks like an indeterminate form, so make it a fraction however you can."

I use that last sentence technique so much, I didn't even know it was an actual thing :D

Parth Sankhe - 2 years, 6 months ago

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