Sign Definition and 596 Threads

Homework Statement Attached Homework Equations The Attempt at a Solution At (-1, -5), moving up along y causes a drop in the value of the function, so the first derivative wrt y is negative. Since the contour lines also get closer in this direction, the function is dropping...

Homework Statement Find the derivative of the transformation x=rcos(theta), y=rsin(theta). Then estimate the cartesian coordinates for r=2.2 and theta=pi(1/6-1/60) The Attempt at a Solution I found the partials with respect to r and theta for both x and y. I also wrote down the...

Homework Statement if z=x+iy and sqrt(z) = u+iv u=±(1/√2)*√(x+√(x^2+y^2 )) v=±(1/√2)*√(-x+√(x^2+y^2 )) How must the signs on these result be chosen? 2. The attempt at a solution I wondered if it was something to do with ensuring √(z) was always positive, but then ruled this out as...

I have a question about this problem in relation to the way the solution manual handles it. Homework Statement A force Fx acts on a particle of mass 1.5kg. The force is related to the position x of the particle by the formula Fx = Cx3, where C = .50. IF x is in maters and Fx is in...

Homework Statement The handle of the hammer is subjected to the force of F = 20. Determine the moment of this force about the point A. http://s3.amazonaws.com/answer-board-image/3214a2db-1a55-4648-b582-5f36f0f34451.jpeg Homework Equations Principle of moments: Mo = FxY - FyX The...

Howdy - We're a small nonprofit that hosts a single annual event. For advertising this event we construct a large sign on a hilltop that's visible from the nearby highway. In years past this sign would last a few weeks before it would be destroyed by wind. Obviously our guess on how strong...

Homework Statement See attachment Homework Equations The Attempt at a Solution Why is it -umg(50)? Why negative? Also I think this has something to do with conservative force and friction, and I'm very confused on this. Any help would be appreciated thanks.

if a gas is expanding,what will be the sign of the work done by it?

since no one answer i edit it again.we got the forumla, v1-v0= the negative integral 0f E dot with dr from 0 to 1. So assume we are moving a positive point charge from infinity against the electric field emits by a positive source charge to location p. since E=f/q, and f dot dr = fdrcos180...

Homework Statement When Bob applies the brakes to his car, it slows uniformly from 20.0 m/s to 0.0 m/s in 4.0 s. How many meters before a stop sign must he apply his brakes in order to stop at the sign? 80 m 60 m 40 m 20 m Homework Equations d=(20+0)/2(4)...

This is not actually a homework question but something I saw in a (economics) journal article and have been having trouble getting. It's very simple so I thought I'd post it here. Define the variable V (implicitly) by: V=b + \int^{rV}_{0} rV dF(s) + \int^{\infty}_{rV} s dF(s), where r...

Until today I learned in geometric optics that Object distance +ve for real object else -ve Image distance +ve for real image else -ve Radius of curvature +ve for if light comes to the surcace from the side lying center of curvature else -ve On the basis of this the lens formula...

Homework Statement A square coil of wire of side length 2a lies in the yz plane. A current I flows through the loop. The x-axis is defined such that it passes through the centre of the loop, with the loop boundaries being at z±a and y=±a respectively. Given that I flows in a direction...

Electric potential --- doubt in sign convention Homework Statement Revered members, I know dV = -E.dx so E = -dV/dx So E should be E = -V/x . But while deriving capacitance of a parallel plate capacitor when dielectric medium is introduced we use E = V/x. But how E = V/x? Homework...

A purple beam is hinged to a wall to hold up a blue sign. The beam has a mass of mb = 6.2 kg and the sign has a mass of ms = 15.1 kg. The length of the beam is L = 2.78 m. The sign is attached at the very end of the beam, but the horizontal wire holding up the beam is attached 2/3 of the way to...

When we derive the relations between image distance(v), object distance(u) ond focal length(f) for mirrors or lenses (1/v+1/u=1/f and 1/v-1/u=1/f respectively), using the concept of similar triangles and alternate exterior angles, in the last step we apply standard sign conventions to get the...

Homework Statement I am currently doing some Hooke's Law problems. While I do not have any trouble with any exercise in particular, I do have trouble with the sign in the equation. Let's say I have a vertical spring and I attached a hanging mass m to it. The string will then stretch a distance...

The problem statement is "each of the four uniform links has a mass m. determine the horizontal force P required to hold them in place in the vertical plane as shown." I attached the solution, but I don't get when a force causes a +/- virtual work.

If I disliked math as a kid, is that a sign that I am not naturally talented in it?? From grades K-12 I never liked math one bit. But now that I am college I find myself much more interested in it. However, I am regrettably a very competitive and pretentious person so I am worried that this new...

1) q(x_{1,}x_{2,}x_{3})= x_{1}^{2}+5x_{2}^{2}+26x_{3}^{2}+2x_{1}x_{2}+10x_{1}x_{3}+6x_{2}x_{3} V=\{x=(x1,x2,x3)\in R^{3}:q(x)=0\} check if V is a subspace of R^{3} and find the basis of V? how i tried: i diagonolized it the representative by rows and columns and i see that q is...

Homework Statement I am integrating sin(x)^3cos(x)^3, I know the technique (I hope) and I get the right equation at the end. But if I ask wolfram alpha what the integral of the equation is and enter 0 into wolfram's answer and also enter 0 into my answer, the answers come out different. If...

Hi All, I am confused about what is meant in the mathematical definition for the energy of a signal. Why is it the integral of the magnitude of the signal squared? ∫(|f(t)|^2) How do I deal with the absolute value sign? I do not have much experience with absolute value signs in...

Here is my question. For example if i am standing on top of the empire state building and i define that to be height=0 and i define the downward direction to be positive. if i drop a mass does its potential energy increase based on my definition of direction? My actual problem was an exam...

I have tablet phone samsung galaxy tab... when I check the signal strength, it shows -82 dbm... I thought it is produced by the Signal PA (Power Amplifier) on the PCB... According to what I know, the signal from the handphone is so weak to reach the nearest terrestrial station on the...

Fast question :I noticed that often the EFE are presented without the minus sign in the source term, (G=kT instead of G=-kT) does that have some reason behind or is it just plain sloppiness?

Homework Statement Calculate the Z-transform of the function x[n] = u[n]-u[-n-1].Homework Equations X(z) = ZT\{x[n]\} = \sum_{n=-\infty}^{\infty}x[n]z^{-n} ZT\{u[n]\} = \displaystyle\frac{1}{1-z^{-1}}, ROC: |z| > 1. ZT\{-u[-n-1]\} = \displaystyle\frac{1}{1-z^{-1}}, ROC: |z| < 1. ZT\{x[n]\} =...

Homework Statement I had a question in my physics class today that was relatively easy but what I was confused about was a misplaced negative sign. "An electron is rotating around a proton at a distance R. The mass of the electron is me and the charge is -e. Find the period." Homework...

Hello, I'm having some issues with plane waves propagating through a medium which is: - linear - spatially and temporally homogeneous - spatially non-dispersive - isotropic - temporally dispersive - passive I know that permittivity, permeability and the k-vector are complex in...

I'm a third year planning to graduate 1 semester early. Last fall, I took 18.5 credit hours and worked 2 jobs (paper delivery and research assistant). I was pretty wasted by the end of the semester. Subsequently, I got depressed the following spring semester and had to drop down to a part time...

Hello all who read, I was reading along in the book Advanced Calculus by Frederick S. Woods today and came upon this technique. I played with it a little on some sample problems, but I still cannot figure out what it has any relation to. My questions I guess are that, (1) what...

what does this simplify to: (-33/2)2/3 I use the exponent rules to multiply the fractions to get (-31) which comes out to -3, but the answer key says the real answer is 3. Is there something important when doing fractional exponent that I'm missing out? Thanks in advance.

I saw this rather odd symbol of the the greater sign on top of the less sign in my lecture notes. I am wondering if there is a name for this symbol and if signifies 'equal to' as well?

Just when you thought it couldn't get any worse: From http://newsblog.projo.com/2011/08/cranston-neighbors-upset-by-si.html" This is very bizarre behavior to be sure... harassing and bullying taken to an extreme... Rhody... :eek:

Problem,the equal symbol "=" in math is overloaded , as is the word "is" in language. Is there a list of all the meanings of = in math and the word is. For instance "is" can mean equal to , or element of a set. Are there generally accepted alternatives to the "=" sign, so one can be more...

Homework Statement if lim f(n) = s , prove that lim (f(n))^{1/3} = s^{1/3}. How do you know that as n approaches infinity, f(n) and s have the same sign. n is just an index in this case and f is not a function but a sequence. The attempt at a solution so we know that |f(n) - s| < epsilon...

Hi all, I've been using Faraday's law to find the EMF in a coil of wire in a changing magnetic field. EMF = -N (change in mag flux/change in time) for N loops I'm finding that the EMF is always positive regardless of whether the change in flux is positive or negative. I'm wondering at...

relative minus sign?? Hi, I have one question for you... to compute the matrix element for the process u d -> u d I want to use full SM, but I have one problem I'll give you the maths. process with W: <ud|(\bar{Ψ}u Ψd)(\bar{Ψ}dΨu)|ud> process with γ: <ud|(\bar{Ψ}u Ψu)(\bar{Ψ}dΨd)|ud> Z and...

Might be a naive question. In many places, specially in the Hubbard model, people use a minus sign before the tight-binding hopping amplitude. What does the negative sign signify for? Any special intention? Thanks.

I have to prove that \left\langle lm | \vec{\hat{r}} \times \vec{\hat{p}} | lm\right \rangle = \left\langle lm | \vec{\hat{p}} \times \vec{\hat{r}} | lm \right \rangle, where | lm \rangle are eigenkets of angular momentum operator \hat{L}^2 And I can't figure out a way to do this...

In question 4 of this paper, I am trying to find the sign of \Lambda Since we have the vacuum einstein eqns G_{\mu \nu}=-\Lambda g_{\mu \nu} we can just contract to get R-\frac{4}{2} R=-4\Lambda \Rightarrow \Lambda=\frac{R}{4} So \Lambda will have the same sign as R Now given the...

Homework Statement solve for x: 5|7-3x|+2=4|7-3x|-1 Homework Equations The Attempt at a Solution 7-3x>0 -3x>-7 x<3/7 {x|x<3/7} quantity is positive {x|x>3/7} quantity is negative I have never solved an equation with more than one absolute value quantity in it and am not sure how to start...

We were having our maths class a weeks ago and while studying quadratic equations our teacher asked us if there was an difference between x^{1/2} and \sqrt{x}. Up until then I had always assumed them to be the same thing. However he said that there was a difference and said that he would tell...

Pfff. I don't even understand what "signing a house" over means. I thought that when our parents die, it would be sold and the proceeds distributed evenly. Or something like that. But he is quite a character. I think he sold me my car illegally, for starters. He's had trouble with the law, is on...

hello i just sign up to thses forum recommended by a friend to help with mu assignment. i posted a few questions to get help on but no replies. how do i get more replies and help thank you

Homework Statement http://img64.imageshack.us/img64/7782/circleb.jpg I'm supposed to find the slope equation of the tangent line to the circle at point A. A = (2, 7) The circle's formula is (x+1)2+(y+3)2 = 25 The center point of the circle is therefor (-1, 3) So the slope from the...

Homework Statement This is more of a conceptual problem I'm having with in a problem. I'm trying to find the phase constant of the equation for a capacitor that is charging at time zero. I'm having trouble with figuring out what sign the phase constant should have. Homework Equations...

Homework Statement consider the differential equation: (x^2 -1)y''+(1/x)y'-by=0 what happens to the equation if the sign of x is flipped? what consequences does the behaviour of the equation when the sign is flipped have on the solutions of the equation? The Attempt at a Solution...

Hello all. I'm trying to figure out how to determine the correct sign of paths and surfaces defined for calculating quantities in electromagnetic problems. For example, say there's a wire in the shape of a rectangular prism along the z-axis with some current density, \vec{J} . Then the...

What does the symbol \underbrace{=}_{\wedge} mean? P.S. : The symbol beneath the equals sign is meant to be a triangle.

From what I understand: P=+iv (current enters through the positive polarity of the voltage, implying that the element is absorbing power) and P=-iv (current enters through the negative polarity of the voltage, implying that the element is releasing or supplying power) I remember reading that...