Limit

Calculus Level 1

lim x sin x x = ? \large \lim_{x\to \infty} \dfrac{\sin x}x = \, ?

1 -1 0 infinite

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4 solutions

For lim x ( sin ( x ) x ) \lim_{x \to \infty} \left(\frac{\sin(x)}{x}\right) apply Squeeze Theorem

1 sin ( x ) 1 ^{-}1 \le \sin(x) \le 1

lim x ( 1 x ) lim x ( sin ( x ) x ) lim x ( 1 x ) \lim_{x \to \infty}\left(-\frac{1}{x}\right) \le \lim_{x \to \infty}\left(\frac{\sin(x)}{x}\right) \le \lim_{x \to \infty}\left(\frac{1}{x}\right)

lim x ( 1 x ) = 0 \lim_{x \to \infty}\left(-\frac{1}{x}\right) = 0

lim x ( 1 x ) = 0 \lim_{x \to \infty}\left(\frac{1}{x}\right) = 0

lim x ( sin ( x ) x ) \therefore \space \space \lim_{x \to \infty} \left(\frac{\sin(x)}{x}\right) is 0 0 . \square

ADIOS!!! \LARGE \text{ADIOS!!!}

Muna Kumar
Apr 14, 2016

Or it can be done like this too.. Put x=1/y. Now as x tends to infinity ,y tends to 0.lim sin(1/y)÷(1/y) Or,lim y.sin(1/y);y tends to 0 Or, 0×sin(1/y) =0

Vikas Yadav
Apr 14, 2016

The Range of sinx is [-1,1] .i.e. it will be a finite value. In denominator it is infinite. Therfore, finite/infinite value will tend to zero.

The problem is , if sin tends to zero then ??

Aniket Sanghi - 5 years, 1 month ago

I = lim x s i n x x \large I = \lim_{x\to\infty} \frac{sinx}{x}

Apply L-Hospital's rule ,

I = lim x d d x ( s i n x ) d d x ( x ) = lim x c o s x = c o s ( ) = 0 \large I = \lim_{x\to\infty}\frac{\frac{d}{dx}(sinx)}{\frac{d}{dx}(x)}\ = \lim_{x\to\infty} cosx = cos(\infty) = 0

cos ( ) 0 \Large{\cos(\infty)\color{#D61F06}{\neq}0}

展豪 張 - 5 years, 2 months ago

How can u say cos infinite is 0.

Aniket Sanghi - 5 years, 1 month ago

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cos infinite is indeed not 0

展豪 張 - 5 years, 1 month ago

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