Infinity Definition and 970 Threads

  1. P

    Actual infinitesimal, actual infinity

    Is there an actual infinitesimal in the way that there is an actual infinity. Or would zero fill that role.
  2. C

    Define negative numbers to be greater than infinity

    http://arxiv.org/abs/0907.1090" :smile:
  3. S

    Showing that a function is C infinity?

    I'm currently reading a book, The Road To Reality by Roger Penrose, and trying to tackle some of the exercises in the process. My knowledge in mathematics is limited, but broad enough to complete some of the exercises. Anyway, one of them wants you to consider the one function...
  4. Loren Booda

    A non-trivial infinity of zeroes with real part one-half

    Other than the Riemann Zeta function, what equation has a non-trivial infinity of zeroes with real part one-half?
  5. N

    Limits as n approaches infinity

    lim n-> infinity of: (n^4 + n^2 + 1)^0.5 - n^2 -1 sin(2/n)/(1/n) (ln(n) + e^n)/(2^n + n^2) If anyone could explain the processes required to obtain the limits of any.. (or all) of these statements, that would be great
  6. E

    What Patterns Emerge When Visualizing Infinity on Non-Flat Surfaces?

    Try drawing this mentally: Start with a circle of radius r, draw n number of points spaced evenly on the circle. at each point on the circle draw another circle of radius r, once again with n number of points. What sort of a picture would one get repeating this process a million times, and as n...
  7. J

    What is infinity minus infinity

    hello i m a new user what is infinity minus infinity
  8. R

    What is the equation that shows infinity times zero equals pi?

    I'm 16 and in high school. I've never taken physics or anything before. I have this equation that shows that pi = infinity times zero Ok. So if u take a circle with a diameter of 1 and draw equal spaced radius' and connect them you get a polygon with all equal sides. the more...
  9. N

    Can the Complex Plane Extend to Infinity?

    Homework Statement Hi all. We we look at z\rightarrow \infty, does this include both z=x for x \rightarrow \infty AND z=iy for y\rightarrow \infty? So, I guess what I am asking is, when z\rightarrow \infty, am I allowed to go to infinity from both the real and imaginary axis? If yes, then this...
  10. W

    Lim (x-> infinity) sinh(x)sinh(e^(-x))

    Homework Statement lim (x-> infinity) sinh(x)sinh(e^(-x)) Homework Equations None really. The Attempt at a Solution L'Hospital?
  11. P

    What is the Limit to Infinity of a Rational Function?

    Homework Statement lim_x->∞ of [√x + 2|x|] / [1 + x] Homework Equations lim_x->∞ of 1/[x^n] = 0 The Attempt at a Solution Hi everyone, Here's what I've done so far: I divided top and bottom by the highest power of x, i.e. x. So: [x^-1/2 +/- 2] / [1/x + 1] And taking...
  12. S

    How do you make the potential zero at infinity, here

    Potential difference is what which makes sense. But calculating the potential difference b/w two points and one of them being infinity, where we define potential to be zero, we can actually find the potential at the point. Fine, agreed. Now, how do you define the potential at infinity to be...
  13. A

    Is infinity a constant or a variable ?

    Infinity can't be a constant because ∞ ± k = ∞ , but a constant changes (its) value when something is added or subtracted. But infinity can't be variable because the definition of variable is "A variable is a symbol that stands for a value that may vary" or stating in simple terms "In...
  14. I

    Solving for sin & cos of -1 ∞: Answers & Explanation

    this isn't homework just wanted to know what the values are. tan -1 (infinity) = pi/2 tan-1 (0) = 0 what is sin -1 infinty and cos -1 infinity?
  15. L

    U-th root of 1/u as u goes to infinity is 1.

    Is this true? n,m\in\mathbb{N} \lim_{n\to\infty}\sqrt[n]{\lim_{m\to\infty}\frac{1}{m}}=\lim_{n\to\infty}\lim_{m\to\infty}\sqrt[n]{\frac{1}{m}}=\lim_{u\to\infty}\sqrt[u]{\frac{1}{u}}=1 Thanks
  16. J

    Find the Limit of X and Y Exponents as n Goes to Infinity

    Homework Statement X \geq Y > 0, find \lim_{n \to \infty} \left(\frac{2X^n + 7Y^n}{2}\right)^{1/n} Homework Equations The Attempt at a Solution I'm not really sure how to do it, but i guess I need to use the fact that \frac{Y}{X} \leq 1 , and so \lim_{n \to \infty}...
  17. S

    Sum of 1/ln(n)^(ln(n)) from n=3 to infinity?

    Sum of 1/ln(n)^(ln(n)) from n=3 to infinity? Does the sum of 1/ln(n)^(ln(n)) from n=3 to infinity converge or diverge? TNX ...
  18. D

    Finding the Limit of an Infinite Sum Series | n->infinity

    how do i find the limit for the following , where n->infinity 1/2 + 3/4 + 5/8 + 7/16 +9/32 +... i see that the numerator starts at 1 and has jumps of +2, giving me all the odd numbers the denominator starts at 2 with jumps of *2 giving all the powers of 2 so i have... + (2n-1)/2^n...
  19. D

    Annoyingly simple problem - rational functions and limits at infinity

    Hi all This is my first post so please be gentle with me! Limit of this rational function as x approaches infinity? f(x) = (x^3 - 2x)/(2x^2 - 10) I was under the impression that if the degree of the polynomial of the numerator exceed that of the denominator then there could be no...
  20. C

    A Definite integral where solution. involves infinity - infinity

    Homework Statement Evaluate the integral. http://www.freeimagehosting.net/uploads/176e17ca2f.jpg Homework Equations http://www.freeimagehosting.net/uploads/3168397520.jpg The Attempt at a Solution http://www.freeimagehosting.net/uploads/3168397520.jpg I am stuck here as the book...
  21. C

    A Definite integral where solution. involves infinity - infinity

    Homework Statement Evaluate the integral. http://www.freeimagehosting.net/uploads/176e17ca2f.jpg Homework Equations The Attempt at a Solution
  22. J

    When to use the residue at infinity

    why is it that we can use the residue at infinity on the methods of contour integration example on wikipedia for the last one? we can only use the residue at infinity when it is a rational function, i.e. the ratio of two polynomials, if I'm wrong when i say this, why?
  23. C

    Is Finitism a Key to Understanding the Infinity in Physics and Math?

    I was reading the wiki on this and found it very interesting and would like to hear what established mathematicians and physicists think about this kind of philosophy. Personally I believe that God(used in reference to the universe itself, am not religious) created infinity and man created...
  24. N

    Could Our Universe Be Inside a Black Hole?

    Let me first say I am in high school and don't understand very much calculus or advanced physics. But through my independent work i have created a theory in which i personally can not find any flaws with. I would ask for constructive critisms on this theory. thanks! It is my understanding...
  25. F

    Finding Limit x -> Infinity of y = 2x^2/(a+2x)

    I need to find the limit x -> infinity of the following: y = x ( (2x/a) / (1 + (2x/a)) ) Simplifying.. y = x ( (2x/a) / ((a + 2x)/a) ) y = x ( 2x / (a + 2x) ) y = 2x^2 / (a + 2x) Is this even right in the first place? because I have no idea how to evaluate the lim x -> infinity.
  26. Q

    Limit as X-> infinity of cos(x)

    limit as X--> infinity of cos(x) Homework Statement Find the limit. \stackrel{lim}{x\rightarrow\infty}cos(x) The Attempt at a Solution As best as I can tell by putting larger and larger numbers in my calculator, there is no limit, as cos(x) just oscillates between (-1,1). So is the...
  27. K

    Find the limit as x approaches infinity of (sqrt(1+3x^2))/x

    Homework Statement Find the limit as x approaches infinity of (sqrt(1+3x^2))/x The Attempt at a Solution I tried using l'hopital's rule, but it gave me 3x/(sqrt(1+3x^2)) which doesn't help me at all.
  28. S

    Understanding Limits at Infinity: Conceptual Difficulties

    so i understand how to resolve a limit at x->oo, but from a conceptual standpoint, i do not get it. for example, limit x->oo, 4x/5x so the answer is 4/5, but oo/oo is an indeterminate expression i understand that if i treat x as a variable, then it makes sense, but still if the example was...
  29. T

    Does the Integral from e to Infinity of 67/(x(ln(x))^3) Converge?

    Homework Statement integral [from e to infinity of ] 67 / (x(ln(x))^3) read as the integral from e to infinity of 67 divided by x times cubed lnx. Homework Equations The Attempt at a Solution i know it converges, but i got the value 67/2
  30. M

    What Happens to the Limit of an Equation as k Approaches Infinity?

    Homework Statement \sum(\frac{1}{\sqrt{ln k +2}-\sqrt{ln k -2})}k as k \rightarrow\infty Homework Equations Root test: (ak)1/k The Attempt at a Solution (ak)1/k = (\frac{1}{\sqrt{ln k +2}-\sqrt{ln k -2}) does it equal 0? since 1/\infty = 0 but its \infty - \infty i would have to...
  31. F

    Problem evaluating a limit as x to infinity algebraically

    1. My problem is such: Find the limit of \lim_{x \rightarrow \infty} \sqrt{9x^2+x} -3x 2. No relevant equations 3. I multiplied \frac{\sqrt{9x^2+x} -3x}{1} * \frac{\sqrt{9x^2+x} +3x}{\sqrt{9x^2+x} +3x} = \frac{x}{\sqrt{9x^2+x} +3x} I am now quite confused as to where to go...
  32. F

    Flipping signs for limits at negative infinity

    Homework Statement \lim_{x \to -\infty} x + \sqrt{x^2 + 6x} Homework Equations The Attempt at a Solution Previous attempt was guessing it was \infty, but I see now my flaw and the actual answer is -3. Somewhere else on the web, might have been this forum, it was said that one could flip the...
  33. C

    How can an infinity series be less than infinity?

    Homework Statement I have a space M which is a sequeces of real numbers \{x_n\} where \sum_{n = 1}^{\infty} x_{n}^2 < \infty How can a series mentioned above be become than less than infinity?? Please explain :confused: Sincerely Cauchy
  34. M

    Finding lim f(x) as x->+/- infinity?

    Finding lim f(x) as x-->+/- infinity? f(x)= x^(5/3)-5x^(2/3) Need to find limit f(x) as x-->+infinity, and x-->-infinity?
  35. R

    What Is the Exterior Angle at Infinity for a Semi-Infinite Strip?

    Suppose we have the following shape in the complex plane: The EXTERIOR of the semi-infinite strip bounded by 0 < y < 1 and x > 0. The two physical angles making up the rectangle have interior angles of 3*pi/2 and thus exterior angles of -pi/2. Now, because the sum of the exterior angles of a...
  36. M

    Can sets be bounded by infinity?

    I cannot remember if infinity is an upper bound for a subset of R? I think so, but I want to be sure before I use it in a proof.
  37. V

    Proving lim (as n -> infinity) 2^n/n = 0

    Homework Statement Prove that lim n \rightarrow\infty 2^{}n/n! = 0 Homework Equations This implies that 2^{}n/n! is a null sequence and so therefore this must hold: (\forall E >0)(\existsN E N^{}+)(\foralln E N^{}+)[(n > N) \Rightarrow (|a_{}n| < E) The Attempt at a Solution...
  38. J

    Introductory Calculus: Limit as x goes to infinity

    Homework Statement What is the limit as x goes to positive infinity of: (4x2+3x+8)/(6x2+5x-7)? Homework Equations The Attempt at a Solution Usually I would factor the top and bottom and see if something cancels, but that doesn't work here. Also l'hopital rule doesn't work...
  39. F

    Find limits for x to infinity with L'Hopital

    Homework Statement For the following function decide whether f(x) tends to a limit as x tends to infinity. If the limit exists find it. Homework Equations f(x)=[xsinx]/[x^2 +1] The Attempt at a Solution I thought about using L'Hopitals rule, so i got: [sinx + xcosx]/[2x]...
  40. stevebd1

    Deriving radial velocity as observed from infinity

    In Wheeler and Taylor's 'Exploring Black Holes', on pages 3-12 and 3-13, the bookkeeper measure of radial velocity (i.e. radial velocity as measured from infinity) is derived. Basically the equation for 'Energy in Schwarzschild geometry' is established-...
  41. K

    Statistics: E(X) = Integral(0 to infinity) of (1-F(x))dx

    "If X is non-negative, then E(X) = Integral(0 to infinity) of (1-F(x))dx, where F(x) is the cumulative distribution function of X." ============================ First of all, does X have to be a continuous random variable here? Or will the above result hold for both continuous and...
  42. K

    Proving Infinity of a Sequence: a(n)=[n+7]/[2+sin(n)]

    Homework Statement Prove that the following sequence (a(n)) has the property that a(n) tends to infinity as n tends to infinity. Homework Equations a(n)=[n+7]/[2+sin(n)] The Attempt at a Solution i tried l'hopitals rule, so i got 1/cos(n)...which wouldn't work. so I am not...
  43. P

    Stability of a system with poles and zeros at infinity

    I have a system transfer function H(s) = 1/(e^s + 10) This system has both poles and zeros at infinity and -infinity. Can anybody tell me if this is a stable system. Thanks.
  44. M

    Proving Uniform Continuity of f(x): Let x in [Infinity, 0)

    Homework Statement let f(x)= (x^2)/(1+x) for all x in [ifinity, 0) proof that f(x) is uniformly continuous. can anyone help me with this problem Homework Equations using the definition of a uniform continuous function The Attempt at a Solution i did long division to simplify the...
  45. S

    Calculating the Limit as x Tends to Infinity of a Cube Root Expression

    Homework Statement calculate the limit as x tends to infinity of: \sqrt[3]{x} ((x+1)^{(2/3)}-(x-1)^{(2/3)}) Homework Equations The Attempt at a Solution using the identity: a-b=(a^2-b^2)/(a+b) ; and dividing top and bottom by x, = lim...
  46. H

    Prove n^(1/n) tends to 1 as n tends to infinity

    Homework Statement Need to prove n^(1/n) tend to 1 as n tends to infinty Homework Equations The Attempt at a Solution Have tried comparing to n^(1/n)=(1+h) and using binomial series but no joy..please help
  47. B

    BOOBIES .actually a question on limits approaching infinity

    BOOBIES...actually a question on limits approaching infinity...please help Homework Statement lim x^2-x^4 x>Infinity Homework Equations i made both of them...e^(2lnx)-e^(4lnx)...then get stuck im allowed to use limit laws, and no l'hospitals rule The Attempt at a...
  48. A

    Find a Function f(x) with Limit at Infinity but no Derivative Limit

    Hello I need to give an example of a function f(x) such that limf(x), as x goes to infinity, exists but the limf'(x) does not. Any help? Thx
  49. A

    Find Limit as x approaches infinity

    1. Find the limit as x approaches infinity of (cos(1/x))^(x^2) attempt at a solution I tried using e to change it's form to e^(ln(cos(1/x)*x^2) and taking the limit of the power, the problem is I'm really stuck at this point with the limit as x approaches infinity of ln(cos(1/x))*x^2...
  50. F

    Find the limit of ln(n)/ln(n+1) as n--> infinity

    can someone help me find the lim as n approaches infinity of ln(n)/ln(n+1) I used L'HOP so it became (1/n)/(1/n+1) -- as this approaches infinity, it's 0/0, and this confuses me. What am I doing wrong?
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