1. N

    Time-continuous signal Fourier transform or series

    Hello, i have a short understanding question on the subject of Fourier Transformation. My task is and here I would like to quote: "A periodic signal is given, calculate the continuous time Fourier transform". On the sketch at the task a rectangle is shown, which has its symmetry axis on the y...
  2. D

    Lotka-Volterra with periodic coefficients differential inequality

    I would like to ask which transformation should I use to recive from this Lotka-Volterra inequality x′=x(a−bx−cy)<x(a−bx), this differential form x(t)\leq \frac{x(T)e^{A(t)}}{1+x(T)\int \limits_{T}^{t}e^{A(s)}b(s)ds}, \text{where} A(t)=\int_T^t a(s)ds.
  3. P

    Periodic table of elements found in other planets of Solar System. Is it possible to discover naturally occurring elements in other planets of Solar System ? I.e. Jupiter, Saturn, Venus, Mars, Pluto, Uranus, Neptune, Mercury. Thanks & Regards, Prashant S Akerkar
  4. P

    Periodic table of elements discussions. 1 What are unknown elements? Is it neither a Solid or Liquid or Gas? The Unknown element cannot be classified in any state of matter? 2 Every element in the periodic table is represented by Square. Do you feel a Circle or any other Geometrical...
  5. P

    Periodic table data in Excel software.

    Do you feel it is useful to have Periodic table data of elements in Excel software? Thanks & Regards, Prashant S Akerkar
  6. H

    Periodic Function

    Hey Forum People, I am doing practice problems for a final. I have a problem finding a function for The amount of electrical power a town consumes at a given time of day is roughly periodic. Hoping someone can get me started on this one. Thanks a lot. Here's the problem. Assuming a...
  7. M

    Even and odd periodic extensions

    Consider the piecewise function, $f(x)=\left\{\begin{array}{r|r}x+4 & 0 < x < 2\\0 & 2 < x < 3\\\end{array}\right\}$ ---------- The odd periodic extension $F^O (x)$ of $f(x)$ is defined as: $F^O (x)=\left\{\begin{array}{r|r}0 & -3 < x < -2\\x-4 & -2 < x < 0\\x+4 & 0 < x < 2\\0 &...
  8. E

    Prove that the function is periodic

    The question is as follows: suppose that x_1(t) is periodic with period T_1 and x_2(t) is periodic with period T_2. Show that the sum x(t)=x1(t) + x2(t) is periodic only if the ratio (T_1/T_2) is equal to a ratio of integers (k_2/k_1). I worked it out but I don't think its correct. my...
  9. J

    Determining the amplitude of the complex periodic function.

    Hi, I am having trouble finding the maxima and minima of a periodic function created by using fourier transform. The problem is I tried to get the derivative of the function, equate to to zero, and solve for the values of x (critical points). The only problem is the value is just one and upon...
  10. D

    Periodic decimal fractions

    Hello! To solve the equations: 1) \frac{1}{x}+\frac{1}{y}+\frac{1}{z}=\overline {0.xy(z)} 2) \frac{1}{x}+\frac{1}{y}+\frac{1}{z}=\overline {0.x(yz)} 3) \frac{1}{x}+\frac{1}{y}+\frac{1}{z}=\overline {0.(xyz)}
  11. R

    Periodic solutions of a difference equation

    One of the exercises I've currently encountered is; "Find all real periodic solutions of the equation y(n+1) = y(n)^2, n \in \mathbb{N}" To me this seems to be a trick question since all I can come up with is the 1-periodic (equilibrium) solutions c_1 \equiv 0 or c_2 \equiv 1. Is there...
  12. O

    periodic spectrum of a cantor system

    Hi, I need to prove that p belongs no the periodic spectrum of T in Homeo(X) iff 1/p is an eigenvalue of the cantor system (X,T) any ideas? regards,
  13. R

    Periodic Solution to Differential Equation

    For each epsilon greater than 0, show that the differential equation x'=(x^2)-1-cos(t)-epsilon has at least one periodic solution with 0 less than x(t) less than or equal to square root of 2+epsilon
  14. J

    Spatial and temporal periods and periodic functions

    A periodic function is one that f(\theta) = f(\theta + nT), by definition. However, the argument \theta can be function of space and time ( \theta(x, t) ), so exist 2 lines of development, one spatial and other temporal: f(\theta) = f(kx + \varphi) = f(2 \pi \xi x + \varphi) = f\left(\frac{2...
  15. E

    y periodic

    Hello!I have a quetion. If we have the differential equation y(x)=(b+5/2)*e^x-3/2(sinx+cosx)-1,which has to be the value of b,so that y is periodic?
  16. B

    System of 2 ODE's with periodic coefficients.

    X'(t) = (a+bcos^2(t))X + (1-bsin(t)cos(t))Y Y'(t) = (-1-bsin(t)cos(t))X + (a+bsin^2(t))Y This is my problem. Obviously this is of the form X' = AX where A is given above and X=<X,Y>. It's a system of 2 differential equations with periodic coefficients. Basically what i'm trying to do is find...
  17. T

    Nth term periodic seq

    I have this sequence and can't seem to creat an nth term for it, any tip on what too look for, in these types of situations. I have: 7,4,7,4,7...... I get this far U_n=(-1)^n(3) never done this befor so not really sure if I am write or wrong. Any advice on how to do this would be great, big...
  18. S

    Show that sin(x^3) is not a periodic function.

    Last question: Show that sin(x^3) is not a periodic function. bye
  19. A

    periodic function??

    if f(x) is periodic then is it necessary it's first derivative and second derivative are also periodic..... if yes then how???
  20. A

    Is it true that continuous and periodic functions on R

    has at least one global extrema, and prove your answer I've tried to find counter-examples but I haven't found any, so I assume it is true - but I have no idea on how to prove it can I have a tip to start ? Thanks