How do you find the limit of sinx / xsinxx as x approaches oo?

1 Answer
Mar 29, 2016

We use squeeze theorem, which says that for three functions g(x), f(x), and h(x)g(x),f(x),andh(x),
If g(x)<= f(x) <= h(x), and lim_ (x->a)g(x)=lim_ (x->a)h(x)=L
then lim_ (x->a)f(x)=L.

lim_(x->+-oo)sin x/x=0

Explanation:

Given that f(x)=sinx/x
We know that sinx oscillates between -1 and +1 for all values of x. Therefore, if we set g(x)=(-1)/xand h(x)=(+1)/x we have located the two functions satisfying the first condition that
g(x)<= f(x) <= h(x) which can be written as

Given that (-1)/x<= sinx/x <= (+1)/x "for all values of " x " in " (-oo,oo)
We know that lim_(x->+-oo)(-1)/x=0 and "also that" lim_(x->+-oo)(+1)/x=0.

It follows from the squeeze theorem that
lim_(x->+-oo)sin x/x=0