1 raised to Infinity becomes finite???

Evaluate \(1^{\infty}\).

Most of the students if asked this question will answer 1, since 11^{\infty} is seems to be equal to

(1×1×1××1)1\times 1\times 1\times \ldots\times 1) with one being multiplied by itself infinite times.

However, more advance mathematics introduces us principle of limits and able to evaluate like cases.

Now, consider this limit

limx0(1+x)1/x\lim_{x \to 0} (1+x)^{1/x} ,

and we all know the limit gives us constant ee.

Consequently, as x0x \to 0, 1+x11+x \to 1 and 1/x1/x \to \infty, so the limit will give us the limit of 11^{\infty}.

Questions:

a) Is 11^{\infty} a finite number?(or somewhat equal to ee as what the arguments stated above)

b) Are there errors in my understandings particularly in my arguments being used?

c)Resolve the argument or give proof/disproof that 11^{\infty} is not equal to one.

Thanks for responding. I am really confused about this.

Note by Mharfe Micaroz
8 years ago

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11 votes

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Comments

On limit studies, 11^\infty is not determined.

I think that happens because this limit depends on who approaches "1" faster: the basis or the exponent. It may result 0 if the exponent is much faster and the basis goes to 1 from above. It may result 0 if the exponent is faster and the basis approaches from below...

So...

a) It is not a number. In fact, \infty is not a real number (maybe an extended one), so the only way to define 11^\infty is using limit process.

b) The error is not in the arguments, but in it's implications for calculus. We just can't define this limit properly.

c) You can find some exemples of limits giving indetermination 11^\infty and in fact may result 0, \infty, 1...

Victor Chaves - 8 years ago

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Sorry, typo: " It may result \infty if the exponent is much faster and the basis goes to 1 from above."

Victor Chaves - 8 years ago

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you know, you can edit your posts.

Matthew Lipman - 8 years ago

Victor, I want to ask you something.

what is the definition of infinity (\infty)?

is \infty the max number or the greatest one? or is \infty something which just extend and neverending? or maybe you have another definition for \infty?

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Many philosophers have made this same question. My nonlinear programming professor said that \infty is a number, such is bigger than any number you can think. Sorry for my grammar.

Francilio Araújo - 8 years ago

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@Francilio Araújo Actually infinity cannot be regarded a number nor any quantity, according to my point of view, rather it is a variable whose value depends upon the conditions where it is used.

Pulkit Singal - 8 years ago

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@Pulkit Singal variable?

hmmm. do you mean that infinity is indeterminate?

indeterminate can be anything, but infinity is just infinity. I think they are different.

hmmm.

ah, yes I know. this webpage

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@Yulianto Indra Setiawan No I don't mean that infinity is indeterminate but something whose value depends upon the situation where it is used (as I sated earlier !). In short I mean it's value can be determined but is variable.

Pulkit Singal - 8 years ago

@Francilio Araújo if \infty is a number, then maybe there are -\infty and ++\infty too.

now draw a circle (for Cartesian proofing) or a sphere (for 3D proofing) and assume the center of the circle or sphere is zero (00), also assume the perimeter of the circle or the surface of the sphere is infinity (\infty). that shape like the Expanding Universe Theory.

it's okay Francilio, grammar isn't important if the other know what you mean. :)

One way to prove the statement wrong is to assume for some time that 1^infinity is equal to some finite number say "k". Now, putting this in expression form, 1^infinity=k , now doing log(to the base 1) on both sides, we will get, infinity = log k, as log k is equal to k which is a finite number, it will lead to contradiction as infinity> any finite number and cannot be equal. So it proves the statement that 1^infinite is either not definite or is either 1. Note:-All the logs have been taken with the base 1.

Siddharth Kumar - 8 years ago

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Log with base one ins not well defined.

If we could do log(to the base 1) on both sides we could do this: 12=132=31^2 = 1^3 \Rightarrow 2=3

Victor Chaves - 8 years ago

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@Victor Chaves Thanks, Victor.

Now I have new knowledge. ^_^

@Victor Chaves but he can make 1=e01=e^0 and use the neperian logarithm. It results 0=k0=k. The problem is, math barely can handle with \infty or 00 (and their correlates) without making some paradoxes, as you can see easily in the barber paradox or the halting problem

Francilio Araújo - 8 years ago

no....this is wrong........log with base 1 is not defined

Pushkar Bajaj - 8 years ago

limn1n=1 \lim_{n \rightarrow \infty} 1^n = 1 but if you are looking for limnf(n)g(n) \lim_{n \rightarrow \infty} f(n)^{g(n)} where limnf(n)=1 \lim_{n \rightarrow \infty} f(n) = 1 and limng(n)= \lim_{n \rightarrow \infty} g(n) = \infty , it depends on the specific f f and g g.

Bart Bosma - 8 years ago

First of all, 11^{\infty}, in this case, is not a number. It is what mathematicians call an indeterminate form (because it can't be uniquely determined what it is).

It could be represented by something of the form limxaf(x)g(x)\lim_{x \to a} {f(x)^{g(x)}}, where f(x)f(x) and g(x)g(x), are functions such that when xax \to {a} (for aRa \in \mathbb{R} or a=±a = \pm \infty), f(x)1f(x) \to 1 and g(x)g(x) \to \infty.

One of the standard ways in which its value can be resolved (and in general, whether it is convergent or divergent) is to convert it into an indeterminate form of 00\frac{0}{0} or \frac{\infty}{\infty} by doing this neat trick:

limxaf(x)g(x)\lim_{x \to a} {f(x)^{g(x)}} = exp(limxalnf(x)1/g(x))\exp(\lim_{x \to a} {\frac{\ln{f(x)}}{1/g(x)}})

or

limxaf(x)g(x)\lim_{x \to a} {f(x)^{g(x)}} = exp(limxag(x)1/lnf(x))\exp(\lim_{x \to a} {\frac{g(x)}{1/\ln{f(x)}}})

These limits can then be standardly evaluated using l'Hôpital's rule. For example, in the case of limx0(1+x)1/x\lim_{x \to 0} {(1+x)^{1/x}}:

limx0(1+x)1/x\lim_{x \to 0} {(1+x)^{1/x}} = exp(limx0ln(1+x)x)\exp(\lim_{x \to 0} {\frac{\ln{(1+x)}}{x}}) = exp(limx01/(1+x)1)\exp(\lim_{x \to 0} {\frac{1/(1+x)}{1}}) (using l'Hôpital's rule) = exp(1)\exp(1) = ee.

Of course, this all changes if by 1 you mean the constant function f(x)=1f(x) = 1. I think that in that case this indeterminate form evaluates to 1 every time.

Petar Veličković - 8 years ago

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You mean this trick is for intederminate form of 11^\infty or 0\infty^0.

Victor Chaves - 8 years ago

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Yes. It also works for 000^0.

Petar Veličković - 8 years ago

To know whether 1 ^ ∞ = 1 or not, we need to understand the meaning of We all know that _ ∞ _ is not defined, but why is it so ?

Rather it should be defined (according to me). Now I tell you something, try it, do it : Ask yourselves a few questions -

  • How many points are there on a line segment of length 2 cm ?
  • How many points are there on a line segment of length 10 cm ?

Of course your answers will be the same, but do you think it should be the same i.e. there are same no. of points on line segment of 2 cm and that of 10 cm but then what's the point of difference between them ??

Pulkit Singal - 8 years ago

First of all, \infty is not a real or a complex number, so you should not appeal to properties of those number systems to evaluate expressions with infinity. You can sometimes study expressions with infinity by interpreting it as a limit, but that is a human reinterpretation of the question.

Even if this question were interpreted as a limit, the most direct translation would be to: limx1x\lim_{x \to \infty} 1^x And this limit does equal 1.

A less direct interpretation would be to interpret it as: lima1andxax\lim_{a \to 1 \text{and} x \to \infty} a^x This expression is undefined unless there's a relationship between a and x.

There are some number systems (such as the surreal numbers) which do include arithmetic properties of infinity, but you will have to be clear about what number system you intend, and understand the properties of that number system when evaluating the expression. In the surreal number system, I believe 1ω1^{\omega} evaluates to 1.

Marcus Neal - 8 years ago

please explain a bit clear even i have the same doubt

pls!!

abhi yellapragada - 8 years ago

1^∞ is an indeterminate term because for limit we take left hand(lhl) as well right hand limit(rhl). For this case lhl is 0 as 1-h where h tends 0 is term smaller than 1 and on repeated multiplication will go on to 0 whereas rhl is ∞ because 1+h where h tends 0 is greater than 1 and on repeated multiplication goes to ∞....

Pushkar Bajaj - 8 years ago

1 raised to any power is 1, always.

Akshat Jain - 8 years ago

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Hello :)

Anglingdewi Suwono - 8 years ago

We already discussed this a week and a half ago. It shouldn't be too far down: Page 3 or so. read that.

Matthew Lipman - 8 years ago

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am i forbidden here to ask this genius people?..

Mharfe Micaroz - 8 years ago

I think everything has 11^{\infty} as their identity.

Look at my example below.

If we have number 22. Then we write like this 2×12 \times 1. After that, we also write like this 2×1×12 \times 1 \times 1, like this too 1×2×1×11 \times 2 \times 1 \times 1 and so on or we simplify like this 2×12 \times 1^{\infty} and like this 1×2×11^{\infty} \times 2 \times 1^{\infty} and so on again.

isn't it?

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u on skype??

superman son - 8 years ago

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Yes, I still trying to be present everywhere.

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