Lazy Limits 3!

Calculus Level 3

lim x 0 ( 1 + sin ( x ) ) ( 1 / x ) = ? \large\lim_{x\to0}{(1+|\sin(x)|)}^{(1/x)} = \, ?

e 2 e^{2} e e e 1 e^{-1} The limit does not exist e 2 e^{-2}

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3 solutions

L = lim x 0 ( 1 + sin x ) 1 x L + = lim x 0 + ( 1 + sin x ) 1 x = lim x 0 + ( 1 + sin x ) 1 x = lim x 0 ( 1 + x sin x x ) 1 x Let x = 1 n = lim n ( 1 + 1 n sin 1 n 1 n ) n = e L = lim x 0 ( 1 + sin x ) 1 x = lim x 0 ( 1 sin x ) 1 x = 1 e \begin{aligned} L & = \lim_{x \to 0} (1+|\sin x|)^\frac 1x \\ L_+ & = \lim_{x \to 0^+} (1+|\sin x|)^\frac 1x \\ & = \lim_{x \to 0^+} (1+\sin x)^\frac 1x \\ & = \lim_{x \to 0} \left(1+\frac {x\sin x}x\right)^\frac 1x & \small \color{#3D99F6}{\text{Let }x = \frac 1n} \\ & = \lim_{n \to \infty} \left(1+ \frac 1n \cdot \frac {\sin \frac 1n}{\frac 1n}\right)^n \\ & = e \\ L_- & = \lim_{x \to 0^-} (1+|\sin x|)^\frac 1x \\ & = \lim_{x \to 0} (1-\sin x)^\frac 1x \\ & = \frac 1e \end{aligned}

L + L \implies L_+ \ne L_- , therefore, the limit L = lim x 0 ( 1 + sin x ) 1 x \displaystyle L = \lim_{x \to 0} (1+|\sin x|)^\frac 1x does not exist.

lim x 0 ( 1 + sin x ) 1 x = e ln lim x 0 ( 1 + sin x ) 1 x = e lim x 0 1 x ln ( 1 + sin x ) = \large \displaystyle \lim_{x\to 0} ( 1 + |\sin x|)^{\frac{1}{x}} = e^{\ln \lim_{x\to 0} ( 1 + |\sin x|)^{\frac{1}{x}}} = e^{\lim_{x \to 0} \frac{1}{x} \cdot \ln (1 + |\sin x|)} = e sin x x = doesn’t exist \large e^{\frac{|\sin x|}{x}} = \text{ doesn't exist} Details. lim x 0 + sin x x = 1 \lim_{x\to 0^+} \frac{|\sin x|}{x} = 1 lim x 0 sin x x = 1 \lim_{x\to 0^-} \frac{|\sin x|}{x} = -1

lim x 0 ( 1 + sin ( x ) ) 1 x = lim x 0 ( 1 + sin ( x ) ) 1 sin ( x ) sin ( x ) x \lim_{x\to 0} (1+|\sin(x)|)^{\frac{1}{x}}=\lim_{x\to 0} (1+|\sin(x)|)^{\frac{1}{|\sin(x)|}\cdot \frac{|\sin(x)}{x}} = e lim x 0 sin ( x ) x x x = e lim x 0 s g n ( x ) = =e^{\lim_{x\to 0} |\frac{\sin(x)}{x}|\cdot \frac{|x|}{x}}=e^{\lim_{x\to 0} sgn(x)} =\nexists

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