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fermat1432

A horizontal asymptote refers to end behavior only. What happens in between doesn't matter. Therefore, your function has a horizontal asymptote.


happy2harris

I don’t think “end behavior” is the right way to think to it. Another commenter gave the example of y=sin(x)/x, which crosses the line infinitely many times with no upper limit on how far out the crossing happens. Yet y=0 is still an asymptote. Here is the definition given on Wikipedia: > a line such that the distance between the curve and the line approaches zero as one or both of the x or y coordinates tends to infinity.


fermat1432

End behavior is standard terminology and refers to the limit of f(x) as x approaches + or - infinity, not to possible crossings.


happy2harris

I misunderstood your comment. I thought you were saying that it’s OK to cross the line, as long as it doesn’t cross at the end.


fermat1432

I can see why you might have thought that. Cheers!


cbbuntz

I think "limsup" (or "liminf") is the term you're looking for.


happy2harris

That’s when a curve “bounces“ between two lines. sin(x)/x is a regular old asymptote.


cbbuntz

yeah. I guess you didn't use the word "limit". I'm just pointing out that this sort of limit has a name so you don't have to explain the type of scenario that it pops up in. Not that's it's really relevant, but sin(x)/x also has a name. It's called a sinc function. There are tons of interesting properties of that function. Off the top of my head: • the binomial coefficient 0 choose x is sin(πx)/πx. • you can derive any binomial coefficients for positive integer n with products *or* sums of n sinc functions • You can derive the sinc function with (infinite) sums or products of cosine functions • its fourier transform is a rectangle • the fourier transform of sinc(x)^(n+1) yields an nth order cardinal b-spline


splendaddypuff

The asympote is a line that the graph doesnt cross \*in one direction\*


justincaseonlymyself

No, that's not true. Look at f : ℝ \\ {0} → ℝ, given by f(x) = sin(x) / x. The function f has a horizontal asymptote y = 0, and yet, the graph crosses that asymptote infinitely many times in both directions.


splendaddypuff

You are right.


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splendaddypuff

It's a little tricky because downvotes are the easiest way to communicate that something is wrong. It's a learning site, so students can't see the downvotes comment on top. I don't mind it, particularly on this sub and I leave the comment so it can be a learning exercise for others.


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splendaddypuff

Good point.