What is Sign: Definition and 594 Discussions

A sign is an object, quality, event, or entity whose presence or occurrence indicates the probable presence or occurrence of something else. A natural sign bears a causal relation to its object—for instance, thunder is a sign of storm, or medical symptoms a sign of disease. A conventional sign signifies by agreement, as a full stop signifies the end of a sentence; similarly the words and expressions of a language, as well as bodily gestures, can be regarded as signs, expressing particular meanings. The physical objects most commonly referred to as signs (notices, road signs, etc., collectively known as signage) generally inform or instruct using written text, symbols, pictures or a combination of these.
The philosophical study of signs and symbols is called semiotics; this includes the study of semiosis, which is the way in which signs (in the semiotic sense) operate.

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  1. M

    Sign problem in laplace transform

    Homework Statement \int_{\pi/2}^{\infty}cos(t)e^{-st}dt Homework Equations \int vdu=uv-\int udv v=cos(t) , dv=-sin(t)dt , du=e^{-st} , u=\frac{-e^{-st}} {s} The Attempt at a Solution \int_{\pi/2}^{\infty}cos(t)e^{-st}dt = \frac{-e^{-st}}{s}cos(t) -\int...
  2. M

    Domain of a Function with Sign Graph

    Homework Statement Find the domain of the function. You will need a sign graph. Answer in interval notation. Homework Equations f(x)= (3)/[(x2-4x)1/2] The Attempt at a Solution No clue - I don't know how to use a sign graph or what the positive/negative results mean as solutions on a number line.
  3. E

    Boost Your Equations: How to Make the Integral Sign Larger - Expert Tips

    Hello, I know that I am asking too many questions these days, but I really need these helps, and I think this forum can do that. My problem is: I have equations that when I wrote using Latex, the integral sign seems very small relative to other terms. How can I make it larger? Thanks in...
  4. D

    When should the plus/minus sign be used when dealing with square roots?

    Ok, I know this question sounds incredibly elementary, but please don't just dismiss it, try to understand what I'm REALLY asking. Ok, say we have x^{2} = 9. I know the answer is x = \pm 3. But I was just thinking about the general rule to this. I was thinking that what really happens is...
  5. D

    How to distribute product sign across base and exponent terms

    I am calculating the likelihood of a hierarchical model and am having trouble distributing the product sign. Here are the two expressions that I'm interested in: Product from j=1 to j_k of: (t_jk)^(sum(Z_ijk) + a_k - 1) and Product from k=1 to K of: (b_k)^(j_k*a_k). The tricky...
  6. D

    How to distribute product sign across base and exponent terms

    I am calculating the likelihood of a hierarchical model and am having trouble distributing the product sign. Here are the two expressions that I'm interested in: Product from j=1 to j_k of: (t_jk)^(sum(Z_ijk) + a_k - 1) and Product from k=1 to K of: (b_k)^(j_k*a_k). The tricky...
  7. J

    The meaning of the sign of the wavefunction in electronic structure

    I’m hoping someone will help me fill in some holes in my understanding of the electronic wavefunction. I understand the electronic wavefunction to be a *complex valued* function of the positions of all electrons in the system. But, most descriptions of atomic orbitals refer to the various...
  8. Phrak

    Do one dimensional vectors have a sign?

    Do one dimensional vectors have a sign? (:devil:)
  9. P

    Maximum and chnage of sign of a function

    Guys Can anyone help me in this? I need a function (cos or sin) maximum at 7Pi/4 and at the same time changes sign under phi->phi+Pi with 0< phi< 2Pi...Thank you
  10. Mentallic

    What is the sign of the integral for the function y=log_{10}x from x=2 to x=4?

    Homework Statement Find \int_2^4{log_{10}xdx Homework Equations Use the change of base formula log_ba=\frac{log_ca}{log_cb} The Attempt at a Solution Using the formula: \frac{1}{ln10}\int_2^4lnxdx =\frac{1}{ln10}[\frac{1}{x}]_2^4 =\frac{1}{ln10}(\frac{1}{4}-\frac{1}{2})...
  11. F

    Solving Force on a Hanging Sign

    hanging sign forces?? Homework Statement PIC IS ATTACHED A businessman is hanging a sign outside his store in the fashion shown in the figure below. The sign has a mass of 50 kg. For a sign of this mass, what is the tension in the wire? The sign is rigidly attached to the wall at the...
  12. O

    Can Electrons Change Spin Sign?

    Hi, Is it possible for an electron to change the sign of its spin (under some interaction)? i saw that some of the calculations in the Ising model assumes that the electron is changing its spin sign if it reduce the energy of interaction with its neighbors Thanks, Ori.
  13. D

    Heres a tough sign question with equilibrium that will be on the test.

    Homework Statement A sign that weighs 168N is supported by 2 ropes, a and b, that make 22.5 degree angles with the horizontal. The sign is not moving, what forces do the ropes exert on the sign. I have 45 minutes to figure this out. Homework Equations I don't know any equations...
  14. D

    Solving series with alternating sign

    is there any other way of solving conditional convergence/divergence for a series with alternating sign, whose absolute values' series diverges? i have a question where i need to solve the following series, \sum(-1)n-1\frac{1}{n - sin(n)} from 1 to infinity i take the absolute value...
  15. L

    How to decide the sign of a potential

    Hi! I'm a new user of this forum, although I've been reading a few threads for a while... Mi question is this: in rational mechanics, how do i decide the sign of a potential? Let me explain better: in some exercises it may happen that a mass particle is subject to both gravity and, for...
  16. E

    What is the Sign Convention for Work Done on a Gas in an Isothermal Expansion?

    Homework Statement One mole of an ideal gas at 300K expands isothermally from a pressure of 2x10^6 Nm^-2 to a pressure of 2x10^5 Nm^-2. Calculate the work done ON the gas. Homework Equations dW = PdV The Attempt at a Solution Following through the integral, it becomes clear that work is...
  17. C

    Differentiation under the integral sign

    Homework Statement I am asked to compute d/dt of _{c}\int^{d} ( _{a}\int^{t} f(x,y)dx)dy for t \in (a,b) for a problem involving differentiation under the integral sign. [a,b] , [c,d] are in closed intervals in \Re f a continuous real valued function on [a,b] x [c,d] Homework...
  18. C

    Power in voltage/current sources, passive sign convention

    Homework Statement Determine which of the five sources in Fig. (attached) are being charged (absorbing positive power), and show that the algebraic sum of the five absorbed power values is zero. I've labelled how I'm referring to the sources in red...
  19. V

    Can Work Done Be Negative and Is Potential Energy Ever Negative?

    Homework Statement Is work done by something always negative and work done on something always positive, or do you determine that by the cos theta portion of the work equation. Also, can potential energy be negative Homework Equations W=Fdcos theta PE=mgd The Attempt at a Solution...
  20. A

    Big integral sign with word 2007

    Hi, everyone! I've been working for a while with the new math editing feature in Word 2007 and find it very impressive. My problem is that the integral sign seems to have a fixed size and I don't know how to scale it vertically to fit, for instance, multiple fractions. I've seen that brackets...
  21. E

    Convex mirrors - Sign convention trouble

    Homework Statement I solved the problem, but upon further observation, I discovered that what I did didn't make sense. (these are rounded numbers, which shouldn't make a difference in my question) do = 13 cm (do is what I solved for in the problem, and according to the online system it was...
  22. P

    Straightforward differentiation, but think I have wrong sign somewhere

    1. Homework Statement , attempt at a solution Please see attached. I'm actually busy with a physics problem, but solving it requires that I complete this part correctly. It's straightforward differentiation, but I think I made an error with my signs somewhere and I can't for the life of me...
  23. H

    Quick sign question for uniform circular motion

    Homework Statement what is the maximum speed with which a 1500kg car can make a left turn around a curve of radius 50m on a level road without sliding? Homework Equations The Attempt at a Solution i already got the answer...but my question is: f_s points left and the...
  24. D

    Sign and Magnitude (Hexadecimal and 8-bit

    First off sorry, but I did away with the automatic formatting. For a homework assignment I need to do a few problems which involved adding and subtracting hexadecimal and 8-bit numbers being added and subtracted. I've done the problems that involve the unsigned numbers fine, but I'm confused...
  25. C

    Question why is there a negative sign

    A particle moves along the c axis. its position is given by the equation x = 2+3t-4t^2, with x in meters and t in seconds. Determine (a) its position when it changes direction and )b) its velocity when it returns to the position it had at t = 0. i understand how to get (a) but for (b) I am...
  26. A

    Engineering Passive Sign Convention in circuit

    Homework Statement Calculate the power in the voltage source for this given circuit: Homework Equations P = \frac{V^2}{R} Or P = - \frac{V^2}{R} The Attempt at a Solution If we take the bottom left corner as the Initial node then and go around the circuit, then the voltage is a...
  27. G

    Dump my bank, sign up w/ a credit union?

    I'm sick of the greed that comes w/ having my money in a big bank. Anyone have their money in a credit union? Is convenience a problem?
  28. H

    Need help with the sign of g in free fall acceleration

    Homework Statement Heather and Jerry are standing on a bridge 50\;m above a river. Heather throws a rock straight down with a speed of 20\;m/s. Jerry, at exactly the same instant of time, throws a rock straight up with the same speed. Ignore air resistance. How much time elapses between the...
  29. Peeter

    Electrodynamics Lagrangian. differences in sign in online references.

    In http://en.wikipedia.org/wiki/Covariant_formulation_of_classical_electromagnetism It is written: \mathcal{L} \, = \, \mathcal{L}_{\mathrm{field}} + \mathcal{L}_{\mathrm{int}} = - \frac{1}{4 \mu_0} F^{\alpha \beta} F_{\alpha \beta} + A_{\alpha} J^{\alpha} \,. a personal...
  30. R

    The sign of Gravitational Potential Energy

    Homework Statement I read this statement: "The gravitational potential energy of a particle at a point with respect to another particle (kept at rest) is equal to the work done by the force which brings them from infinite separation at that point, without gain in kinetic energy." Then I tried...
  31. M

    Solve Hanging Sign Problem: Tension in Two Ropes

    1. Ok, i need help on this question: Find the tension in two ropes holding up a sign. The sign weighs 59 kg. The hypotenuse of the ropes holding the sign is the ceiling, with the left angle of 24 degrees, and the right is 72 degrees. 2. How do i solve this? 3. i think i start...
  32. B

    How Far Can Professor Fich Move Before Exceeding the Rope's Tension Limit?

    Homework Statement 3B. A uniform wooden sign of mass 4.0 kg hangs beside a building wall. The sign is 2.00 m high and 4.00 m wide. It is supported by a hinge at P, that is midway up one edge, and by a light rope that is attached exactly three-quarters of the distance across the upper...
  33. B

    Divergence theorem - sign of da

    Homework Statement This is just a general question. My fundamentals aren't very solid because I'm studying on my own at the moment. \int_V (\triangledown \cdot \bold{v}) dV = \int_S \bold{v} d\bold{a} I am trying to find out the sign of the area integral on a surface defined by spherical...
  34. C

    Why we call 'Passive' sign convention?

    Hello, It's my first time login. I'm not good at english. Of course, I'm not native speaker. I wonder why we call 'passve' sign convention. have a good day. :)
  35. M

    Why is the sign in the formula Δy=VoyT - (1/2)at² negative in this problem

    Homework Statement A placekicker must kick a football from a point 36.0 m (about 40 yards) from the goal, and half the crowd hopes the ball will clear the crossbar, which is 3.05 m high. When kicked, the ball leaves the ground with a speed of 20.0 m/s at an angle of 53.0º to the horizontal...
  36. A

    What force do ropes exert on a sign

    Homework Statement A sign that weights 648 N is suspended by two ropes that make an angle of 38o with the horizontal. What force does each rope exert on the sign? Homework Equations A + B + W= 0 Fh= F cos x Fv= F sin x The Attempt at a Solution This is how my textbook says to...
  37. A

    [Q] Sign of wavefunction in PIB

    Dear all, I have a question about the sign of Schrodinger equation in particle in a box. What's the meaning of the sign (like -, +) of wavefunction in particle in a box? Can anybody explain that? Thank you.
  38. S

    Hanging sign question - equillibrium (with picture)

    http://img355.imageshack.us/my.php?image=picture12ri5.jpg a beam is coming vertically from the wall, and a cord is coming diagonally from the wall. they are both supporting a signhanging from the end. what is the angle of the cord? i don't even know where to begin.
  39. D

    Sign of permittivity/permeability

    Hi. I have a book called "Electrodynamics of Continuous Media" where it is stated that for a passive, lossy material, the imaginary part of the permeability and permittivity must always be positive. But I don't see why. Why is it not OK for one of them to be negative, if the other one is...
  40. K

    Find the Distance and Sign of Charge Q for F1 = F2

    Charge 1 is located along the x-axis and has a magnitude of +1.6E-6C and Charge 2 is located 1m away from charge 1 with a magnitude of -4.8E-6C. A third point charge of magnitude Q is brought from far apart and placed on the line joining the two charges and at a point where the charge q...
  41. N

    What Does a Negative Current Reading Indicate About Ammeter Connections?

    Homework Statement There is a basic circuit set up with just a resistor and an ammeter. If you put an ammeter into the circuit and a negative current is measured what does that mean in terms of the low and high ports of the Ammeter (a digital multimeter in this case) The Attempt at a...
  42. D

    Sign of Wavenumber: Electromagnetic Material

    Hi. In electromagnetics, a material(linear,isotropic,homogenous) with constitutive parameters \epsilon and \mu has the wavenumber k^2=\omega^2\epsilon\mu. Consequently k=\pm\omega\sqrt{\epsilon\mu}. Does this mean that \omega can actually be negative, and if so, when is it the case? It seems...
  43. K

    Quadrant determines the functions sign?

    Hello! In my book we have defined trigonometric functions for all angles. Everything is pretty much the same as when we were using acute angles (same ratio of sides), except that in a quadrant one trigonometric function might be positive, another might be negative, so on. The book has a table...
  44. E

    Solve the fallowing by factoring and making appropriate sign charts.

    Homework Statement Solve the fallowing by factoring and making appropriate sign charts. 2x^2+4x\leq3 Homework Equations The Attempt at a Solution It simply does not factor the way I want it to(unless I did something wrong). I don't think it wants me to use the quadratic formula, and...
  45. N

    Missing minus sign - Motional EMF

    Homework Statement An infinitely long conductor carrying a current I in the positive z-direction lies on the z-axis. A conducting triangle of wires lies in the yz-plane, which moves with a speed v in the positive y-direction. The following figure shows the situation on time t = 0: a)...
  46. R

    Moment of inertia of a sign consisting of ring and rectangle

    [SOLVED] Moment of inertia of a sign consisting of ring and rectangle Homework Statement A sign is formed from two uniform discs,each of mass 0.25kg and radius 0.2m,rigidly,fixed to a uniform rectangular lamina ABCD at A and D. This dis attached at A has diameter AE and BAE is a straight...
  47. R

    Solving the Opposite Sign Puzzle: How to Get the Right Answer

    Can someone please show me how to get this. http://users.on.net/~rohanlal/Untitled-3.jpg I get the same answer but the sign of everything is the opposite.
  48. C

    The + sign above the photodiode, what does it mean?

    I don't really have much knowledge of electronics and kindly seek your helps. The + sign above the photodiode, what does it mean? Does it mean I have to connect the cathode to the ground?? Then, about the direction of the current, why does the current flow from cathode to anode? I...
  49. redtree

    Sign convention in the space-time 4-vector

    What is the rationale for the sign convention in the space-time 4-vector? How is it related to the sign convention in the energy-momentum 4-vector, if at all?
  50. F

    Predict sign of partial derivatives

    Homework Statement The temperature T at a location in the Northern Hemisphere depends on the longitude x, latitude y, and time t so we can write T=f(x,y,z); time is measured in hours from the beginning of January. Honolulu has longitude 158 degrees W, and latitude 21 degrees N. Suppose that...
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