







Is infinite a number? 
20170318 

Divyansh pose la question : Is infinite a number? If yes why as i think that numbers are used for counting but infinite is undeterminable? Penny Nom lui répond. 





An inequality 
20140125 

LANELL pose la question : this is a problem to solve: 1/3 + 2/7 >=x/21  part of the answer is (oo)
not exactly that similarit is on a calculator as a symbol sure you know what it is I am talking about the x will be a number Penny Nom lui répond. 





Extended real numbers 
20111212 

Justin pose la question : Hi there, I was wondering does +infinity=+infinity in the extended real number system? Basically, I was wondering does +infinity=+infinity since infinity and any extended real number (except +infinity) are less than +infinity?
Sincerely,
Justin Robert Dawson lui répond. 





1 divided by 0 and infinity 
20111024 

ritika pose la question : we say that one divided by zero gives us infinity, then why zero multiplied by infinity does not gives us one????????????? Robert Dawson lui répond. 





The number of points on a line is equivalent to that of a surface 
20110324 

Gary pose la question : I I was reading about how the number of points on a line is equivalent to that of a surface. This was done by taking any point on a line then taking alternating digits and making them as points on an x and y axis therefore points on a surface.The problem is as i see it if you just take a line then hold it over a surface you have just put the points on the line in a one to one correspondence with the points directly under it on the surface.Now you have all the rest of the surface which cannot be mapped onto the line since it is already used up.What am i missing? Penny Nom lui répond. 





1/0 and 2/0 
20110211 

Dixit pose la question : How are the infinite number obtained by dividing 1 / 0 and 2 / 0 are different? Penny Nom lui répond. 





Ascribing a value to 1/infinity 
20091119 

Jack pose la question : Hello, and, in advance, thanks for answering.
I came across the problem of ascribing a value to 1/∞ (one divided by infinity) recently, I heard many things:
that it is infinitesimally small (i.e. .0000000000...1 the most intuitive), that it is 0 (the most ludicrous of them
all in my mind), and that it is not definable (which makes the most sense, although is a bit of a let down).
I know that lim (x>∞) 1/x = 0 and this is often used as an argument for all three possibilities. So
what's the ruling on this? And, I know this question has already been answered, but for a little modification;
is there any way to prove the answer that seems to be the most prevalently used (not definable as ∞ is a concept)
with mathematical logic? Or is it just because of the definition of ∞? Robert Dawson lui répond. 





Cardinality of infinite sets 
20090901 

Brian pose la question : I was reading an answer to a question on your site regarding infinite sets (http://mathcentral.uregina.ca/QQ/database/QQ.09.01/carlos1.html), and I think they may have got the answer wrong.
I his example, he claims that the set of real numbers BETWEEN 0 AND 1 is larger than the set of positive integers.
Please correct me if I am wrong, but I believe those two sets are  pardon the expression  equally infinite. For any integer, there is a corresponding real number between 0 and 1, and vice versa.
For instance, using the decimal as a "mirror", you can create a mirror image of any real number between 0 and 1 as an integer (i.e. 0.1234 gets mirrored as the integer 4321  I could write it out algebraically, if you want, but you get my point)
Am I wrong?
Thanks,
Brian Victoria West lui répond. 





An infinite set 
20090807 

Islam pose la question : How can I prove that the set of all odd natural numbers is an infinite set. Thank you. Robert Dawson lui répond. 





The extended real number system 
20090630 

Justin pose la question : Hi again, thanks a lot for answering my previous question! I was also just wondering again if the extended real number system has a potential or actual infinity because it includes positive infinity as a point that exists at the end of it?
All the Best,
Justin Robert Dawson lui répond. 





Potential infinity and actual infinity 
20090629 

Justin pose la question : Hi there, I was just wondering what is the difference between the potential infinity and actual infinity in math? Thanks a lot for your help with this question!
All the Best,
Justin Robert Dawson lui répond. 





Dividing infinity by infinity 
20090624 

Justin pose la question : Hello again, I just had one other question nagging question about infinity. I read this article on "Types of Infinity" on Paul Hawkins calculus website and he stated that one infinity cannot be divided by another or that the answer is inderterminate because fundamentally infinity comes in different sizes with respect to infinite sets and that this applies also to calculus. And so I was wondering (if this is true) is this why when you divide infinity by infinity (in the extended real number system) the answer is indeterminate since fundamentally one inifnity is larger than another like in infinite sets or is there another reason? Thanks sooo much for answering my question again! I greatly appreciate it!
All the Best,
Justin Robert Dawson lui répond. 





Is one Infinity larger than another in the extended real number system? 
20090624 

Justin pose la question : Hello there, I was wondering if one infinity is larger than another in the extended real number system (just like in the transfinite ordinals and cardinals with respect to infinite sets) or are all infinities the same size in the extended real number system? Thanks sooo much for answering my question! I greatly appreciate it!
All the Best,
Justin Robert Dawson lui répond. 





Prove that the set of all positive odd integers is an infinite set 
20090620 

Nazrul pose la question : How can I prove that the set of all positive odd integers is an infinite set.
Thank you in advance. Victoria West lui répond. 





Omega 1 
20090603 

Justin pose la question : Hello there, I was just wondering if the infinity in the extended
real number system is the same as w1 (or Omega 1, the order
structure of the real numbers) in the transfinite ordinals? Thanks
so much for your help with this question, I really appreciate it!
Sincerely,
Justin Robert Dawson and Harley Weston lui répond. 





Infinity and AlephNull 
20090414 

Justin pose la question : Yes, I am reading the Paul Halmos book on Set theory, thanks for telling me how to get it! I was just wondering from your last answer though if the positive real infinity of calculus then corresponds to Alephnull? I am sorry if this is a similar question to the one I asked before but I was just wondering about this!
All the Best,
Justin Robert Dawson lui répond. 





Positive real infinity and Alephnull 
20090409 

Justin pose la question : Hello, I was just wondering why does the positive real infinity correspond to Alephnull? Thanks a lot for answering my question!
Justin Ami and Robert Dawson lui répond. 





Infinite sets and infinite limits 
20090306 

Justin pose la question : Hello, I know I have asked a similar question before but I was just wondering if set theory applies to the lim x>0, y=1/x=infinity and if so, what type of infinity would it be? Thanks a lot for your help with this question!
Regards,
Justin Robert Dawson and Harley Weston lui répond. 





More on cardinal numbers 
20090218 

Justin pose la question : Hello again, I was just wondering that since the rules of Cantor's cardinal numbers in set theory do not apply to the infinity obtained by limits in calculus (ex. x>0, y=1/x=infinity), does that mean that this infinity is the largest quantity in both calculus and mathematics?
Justin Robert Dawson lui répond. 





How can other infinites can be larger than each other? 
20090217 

Justin pose la question : Hello again, I was just wondering even in the context of set theory, how can other infinites can be larger than each other, I thought infinity itself is the largest possible quantity?
Justin Victoria West and Robert Dawson lui répond. 





More on infinity and Set Theory 
20090217 

Justin pose la question : I greatly appreciate your help I was just wondering from your previous answer, why doesn't Cantor's cardinal numbers in set theory apply to the limit x>0, y=infinity?
Justin Robert Dawson lui répond. 





Infinity and Set Theory 
20090217 

Justin pose la question : I was just wondering is the limit x>0, y=1/x=infinity, the biggest uncountable infinity according to Cantor's cardinal numbers in set theory?
Justin Robert Dawson lui répond. 





An integral from 1 to infinity 
20090124 

Ray pose la question : Determine the area bounded by the xaxis and the curve y=1/(x^2) from x=1 to x=infinity.
A. 1.00
B. infinity
C. indeterminate
D. 2.00 Harley Weston lui répond. 





Limit as it Approaches Infinity 
20080729 

mary pose la question : i was trying to find the limit of this problem
the limit as x approches infinity of x minus cosx divided by x
lim xcosx/x
x>oo Harley Weston lui répond. 





1/2 of infinity 
20080516 

Pamela pose la question : Hello. My question was posed to me by my husband, who says he knows the answer and that there is an answer....I have tried to research it myself but to no avail. Here is the question, as he posed it to me.
?? = 1/2 of infinity. Stephen La Rocque, Penny Nom and Claude Tardif lui répond. 





Zero divided by infinity 
20080503 

ANNE pose la question : There was a question about what do you get when you divide Zero by infinity. There was an example using Potatoes. Could someone please explain a little bit more in detail, so that I can help my son who has Schizophrenia understand. He is big into Mathematics and is consumed by this question.
Thankyou so much,
Anne Penny Nom lui répond. 





Limits as x approaches a constant 
20070625 

Mac pose la question : can you please tell me what is the reason they say "denominator is a negative quantity"
in the solution 11 and "denominator is a positive quantity" solution 10 ??
If i guess correctly, for solution 10, its because of x^2 in the denominator. Penny Nom lui répond. 





1/infinity and 1/0 
20060304 

Evan pose la question : I was thinking the other day when i was in math class that when you divide 1 by say n you'll get 1/n. As the value of n increases the smaller the number you get. So if you divide 1/infinity would that equal zero? And if that is true then would 1/0=infinity be true also? Penny Nom lui répond. 





0.999..., asymptotes and infinity 
20041217 

Mike pose la question : My Name is Mike and I teach high school. I had a student ask me to explain why .9 repeating is equal to 1. Then he asked me about an asymptote, or why a parabola or any other curve for that matter can continually approach a value (like 1) and yet never attain a value of 1. He is thinking that these two should represent the same concept and yet they contradict each other. Do you have a solid explanation for him? Of by the way he is a 7th grader. Great little thinker!!!!! Claude Tardif and Harley Weston lui répond. 





Different infinities 
20040527 

Plober pose la question : How can I explain to a friend (in a bar, using as a pen and a paper napkin) that the integer's infinity is 'smaller' than the irrationals's one? The demo I tried was that you couldn't match the integers with the real numbers between 0 and 1 (that 0.xxxxx replacing the Nth number from a different one... that demo), but she used my argument >: saying that you can add one to the integer's infinite, and the number I was creating was only one more...
I can't think of any other way, and I KNOW the real's cardinality is greater than the integer's one Claude Tardif and Penny Nom lui répond. 





x^x^x^x^... 
20040123 

Ryan pose la question : you have a number say x and it is to the power of x which is to the power of x and so on infinite times like x^x^x^x^x^x^x^... i have to figure out what x is so that the answer is always 2 Penny Nom lui répond. 





Dividing zero by infinity 
20040108 

Jason pose la question : What do you get when dividing zero by infinity? Our Calculus teacher was pretty sure that the expression was indeterminate from. However, if this is so...Why? Zero divded by any number (except zero) is zero, true. Any number (except infinite) over infinite is zero. So, why isn't Zero divided by infinite zero. A simpler way if I had 4 potatoes and was to split them among 2 friends, each friend would get 2 potatoes. However, if I had 0 potatoes and split them a infinite number of ways, each person would still have 0. Explain please! Penny Nom lui répond. 





0/0 
20030925 

Thomas pose la question : How is 0/0 ever defined. Penny Nom lui répond. 





What is larger than infinity? 
20030112 

Dana pose la question : What is larger than infinity? Claude Tardif and Harley Weston lui répond. 





Repeating decimals 
20030108 

A student pose la question : If k=.9repeating, and 10k=9.9repeating then 10kk=9k, k=1 therefore .9repeating=1 and 1/3=.3repeating 3x1/3=.3repeatingx3, 3/3=.9repeating, therefore 1=.9repeating It would seem to me that .9repeating approaches one but never quite makes it. Can you clarify? Penny Nom lui répond. 





Can a infinite set be smaller than another infinite set? 
20011129 

Carlos pose la question : Can a infinite set be smaller than another infinite set? If so why? Chris Fisher and Penny Nom lui répond. 





Asymptotes 
20011109 

Frank pose la question :
given the function: f(x) = (x^{2}) / (x1) the correct answer to the limit of f(x) as x approaches infinity is: y = x+1 all math references point to this answer and the method they all use is long division of x1 into x^{2} however if one were to multiply both the numerator and denominator by 1/x and then take the limit, one gets: y=x how can the descrepency between the two answers be explained? Chris Fisher and Penny Nom lui répond. 





Infinite sets 
20000412 

Brian Provost pose la question : Here's the deal: There are an infinite amount of integers (1,2,3...). Agreed? There are an infinite amount of even integers, too (2,4,6...). Agreed? By convention, infinity equals infinity. Yet common sense tells us there are obviously more integers than there are even integers. Prove this to be true mathematically. Harley Weston lui répond. 





Infinity 
19990908 

Richard Tracy pose la question : In order to transverse from point A to point B one must first cross the halfway point (C). Additionally....One must also pass another halfway point labeled (D) in order to get to the halfway point of (C). There is also point (E) which is the halfway point between A and D. We have to assume that there are an infinite amount of halfway points points between (A) and (B). My understanding of infinity is something that goes on forever. But how can one expect to traverse over infinity in a finite amount of time? Will we never reach (B)? Walter Whiteley lui répond. 





Infinity Symbol 
19990713 

Mark E. Kelly pose la question : There is a symbol that looks like a sideways 8 that is used to represent infinity. Does it have a name? Doug Farenick and Penny Nom lui répond. 





Indeterminate forms 
19981211 

R. Dixon pose la question : What is the correct evaluation of infinity/0 ? I've checked three different math sites. One says definitively, that infinity/0 is "not" possible. Another states that infinity/0 is one of the indeterminate forms having a large range of different values. The last reasons that infinity/0 "is" equal to infinity. Walter Whiteley and Harley Weston lui répond. 





Limited area and unlimited perimeter. 
19971128 

Rosa pose la question : There is a figure, it has unlimited perimeter but has limited area , what is the figure and how to draw it ? Thank you very much! Harley Weston lui répond. 





Division by zero 
19970214 

Linda Hood pose la question : I am a college student and have been asked to explain and figure out why we can't divide by zero. Chris Fisher lui répond. 

