Tuesday, January 12, 2016

calculus - What is the value for limxtoinftyfracsinxx?




What is the value for lim?




I solved it by expanding \sin x as



\sin x = x - \frac {x^3} {3!} \dotsc



So \lim \limits _{x\to\infty} \frac {\sin x} x = 1 -\infty = - \infty,



but the answer is 0. Why? What I am doing wrong?


Answer



Yes , the answer is 0 .




One way to see this is by using the inequality :



\left |\frac{\sin x}{x}\right | \leq \frac{1}{x} when x>0 (this happens because |\sin x\ | \leq 1 )



When x \to \infty we have \frac{1}{x} \to 0 so the limit must be 0 .


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