Sign Definition and 579 Threads

Homework Statement Hi there. Well, I've got some doubts on the partial derivatives for the next function: f(x,y)=sg\{(y-x^2)(y-2x^2)\} Where sg is the sign function. So, what I got is: f(x,y)=f(x)=\begin{Bmatrix}{ 1}&\mbox{ if }& (y-x^2)(y-2x^2)>0\\0 & \mbox{if}& (y-x^2)(y-2x^2)=0\\-1 &...

A negative number has the minus sign as its own intrinsic operator. Has anyone thought of using the divide symbol in a similar way, and has there been any attempt to standardize this throughout math? For example (assuming / is the divide symbol): /5 = reciprocal of 5 = 1/5 = 0.2. It saves...

Homework Statement suppose an object A is placed on a horizontal frictionless table, and connected with a light inextensible string with a light, fixed pulley at the edge, and object B is only pulled by the vertical string that connected to a pulley. I tried to set the acceleration up and...

Hi, I am from Belgium so i apologize for my English, I have encountered a problem, i don't understand how to set up the sign analysis of irrational functions, so i decided to find some information on the internet, but the problem is that I am not sure if "sign analysis of irrational functions"...

Hello, I have a doubt regarding dot convention in magnetically coupled circuits. In book A, the following is stated: But in book B, this is stated: In book B, why the inducted voltage of the second mesh (-j w M I1) has that negative sign ? According to dot convention, it is supposed that...

How would you solve this without using decisional blocks?

I am using Latex for typesetting technical document. The default \int command produces the integral sign in somewhat slanting style. But I need the integral sign which look straight as I get in Mathtype software. Even though one may feel, why can't I just accept the default style of integral...

why diode has such a sign?? by the bottom sketch we have the diode to be short circuit but if we look at the upper sketch we see that the current (ie electrons) flows from the plus p side for diode to be short circuit we ned to have the electrons flow to the n side not to the p side...

Hey i stumbled over a problem which i can't solve: f is a continuous function on [a,b] and F_n is recursive given through: F_1(x)=\int_a^x f(t) \ dt and F_{n+1}=\int_a^x F_n(t) \ dt I have to proof that F_n looks like this: F_n(x)=\frac{1}{(n-1)!}\int_a^x (x-t)^{n-1} f(t) \ dt...

Homework Statement A 120-cm-wide sign hangs from a 5.4 kg, 200-cm-long pole. A cable of negligible mass supports the end of the rod as shown in the figure. What is the maximum mass of the sign if the maximum tension in the cable without breaking is 380 N?Homework Equations \Sigma \tau = 0The...

We were taught in the vibrations and waves lecture course that the solution to the wave equation for traveling waves is of the form ψ(z,t) = Acos(wt-kz). In the Electromagnestism course we learned that EM waves are traveling waves and have the solution E = E0cos(kz-wt). I know that changing...

Homework Statement a uniform 2kg horizontal beam is 50cm long is bolted to a wall and supports a 5kg sign. calculate the tourqe produced by the combined weight of the beam and the sign about where it is mounted to the wall. Homework Equations tourqe = F x Perpendicular distance The...

0\leq x,y\leq1, \,\,a>0,\,\, \phi_{a}(x,y)=\frac{1}{a}\,x^{(1-a)/a}+\frac{1}{a}\,y^{(1-a)/a}-\frac{1}{a^2}\,(x\,y)^{(1-a)/a} . In which case depending on the value of the parameter "a" ,the function \phi_{a}(x,y) \geq 0 . Thanks

As most of us know, President Obama intends to cut NASA's funding to such an extent that the Constellation project is going to be cancelled. What is implicated in this decision is the fact that it will leave the USA without any space vehicle of any kind to get into space. This means the...

If you have a phasor that has a negative magnitude (ie -3<38degrees) what is the best presentation. I believed it was just erasing the - sign and adding or subtracting 180degrees. Correct me if wrong

Homework Statement Example 3.13 : Example 3.1 Homework Equations v=u+at S=ut+1/2at2 v2-u2=2aS The Attempt at a Solution I know the solution is in front of me, that's ok but I have a confusion regarding negative & positive signs. In both the examples something is moving vertically upwards...

I have been wondering why we take work done on the system +ve in chemistry while -ve in physics. Similar difference exist for many other quantities. Can you explain why the difference exists?

The integral sign \int can have two meanings: (1) It indicates the Riemann sum, in which we don't actually integrate, but add the rectangles under the curve. (2) It indicates the actual integration, in which we integrate (i.e. antidifferentiate) the function, either just to find the...

Homework Statement I have to evaluate the numerical value of the derivative of the following integral for x=1 \int_{0}^{\ ln\ x}\ e^{\ -\ x\ (\ t^2\ -\ 2)}\ dt Homework Equations The formula for differentitation under integral sign. The Attempt at a Solution The upper limit...

Looks like \triangleq. I first came across it on the wikipedia article for Lie derivative. http://en.wikipedia.org/wiki/Lie_derivative#The_Lie_derivative_of_a_function

Hi all- Can anyone offer any insight into a problem I've noticed for years but don't know how to solve? I'm a self taught neon tube bender. I am not an electrician or electrical engineer. Through the years, I've noticed neon tube, fluorescent lamp, transformer and ballast failure more often...

I'm calculating the capacitance of a set of spherical shells of radii b > a. To do this, I place a charge +Q on the inner shell and -Q on the outer shell so that I get the electric field vector pointing outward \vec E = \frac{Q}{4\pi\varepsilon_0} \frac{\hat r}{r^2}. Finding the...

-ve sign in expression of "induced emf" What is the concept behind putting negative sign in: e=[SIZE="2"]-[rate of change of flux] Which direction does it signify?? How does direction affect the equation? How and where can we use negative sign in other expressions of induced emf??

the telegan law basically states that the total sum of power is zero. my prof proved lik this: we choose a node (a point where more then one currents come together) and decide that the voltage on that node to be zero. we designate the voltages on the nodes to be e_k J_k is the current...

Homework Statement A 2 kg disk traveling at 3 m/s strikes a 1 kg stick of length 4 m that is lying flat on nearly frictionless ice .Assume the collision is elastic and the disk does not deviate from its original line of motion. Find the translational speed of the disk, the translational...

Homework Statement A gas spontaneously expands into an evacuated container. Indicate whether delta T, delta E, delta H, delta S, q, w, and delta G are positive, negative, or zero. Homework Equations delta G < 0 (spontaneous) delta G= delta H - TdeltaS delta E= q + w [/B] The...

Hi all, hope I'm not intruding or posting in the wrong place, and I apologise in advance if I have. 1st, I am not a grad student, simply a guy with the desire to invent things and fix stuff till it's broken. A few of my projects include a solar tracking system, which analyses webcam images...

Does anyone know how to solve for x in the following equation: x + \sqrt{x} = 6 I don't know how to solve for x with eq'ns like this, and I'm studying inverse fxns right now, so I'm told that's what I'm supposed to do. The square root sign is throwing me off. The first time I tried...

Hi, I hit a 4x4 post holding a streetsign up on a country road. I guess I was doing about 20 or 30 when I went off the road and struck the sign. It snapped the 4x4 in half at impact point and then toppled onto and almost into my windshield. I am looking for a physics formula to help...

I need help understanding the sign of voltages across an inductor. Homework Statement There is a current source providing current I to a resitor of resistance R in series with an inductor of inductance L, of which the other end is grounded. The voltage at the current source is V1 and the...

Good evening, (NOTE: This post got a little long; I hope someone has enough patience to read it.) I self-teach physics to myself, but I don't have a complete book (I only have "Volume 2: Gravity, Waves and Thermodynamics" of "Physics" by Paul Tipler). Volume 1 discusses work and energy, but...

Homework Statement Here are two, unconnected example problems, having to do with quadratic inequalities. I'm confused b/c I understand how to solve them with an = sign, but as inequalities the book shows extra steps where signs get reversed and a total of ~ 4 possible answers come up instead...

hello. I am wondering if there is anyway to retrieve a painted image from a galvanized sign that has rusted over. The original logo/name was likely painted in black stencil over galvanized sheet metal. I have not seen it in person yet, but from pictures it looks like image is gone and whole...

[b]1. Homework Statement [http://img44.imageshack.us/img44/1104/58339946.jpg ][/URL] [b]2. Homework Equations [F=k*abs(q1)*abs(q2)/r^2] [b]3. I understand the equation, but I am having trouble with my signs and also how to include the distance in the equation. I know that the...

Homework Statement If I have the standard sign function defined on R is the corresponding Fourier series the standard Fourier series with plus/minus in front respectively? Homework Equations The Attempt at a Solution

Homework Statement Attached is a diagram of the problem. A 28kg sign is suspended by two massless cables. Find the tension in each. Homework Equations The Attempt at a Solution I'll call the cable at 57 degrees T1 and the other cable T2. T1∙cos 57 + T2∙cos 36 = 9.8m/s2∙28kg T1∙cos 57 +...

Homework Statement 1) Q. Which of the elements follow the passive sign convention? (psc) http://img401.imageshack.us/img401/3092/pic1r.gif v1 = +5 (V) i1 = +2 (mA) v2 = -10 (V) i2 = +500 (µA) v3 = +1 (V) i3 = -3 (mA) 2) Q. Which of the elements follow the passive sign...

Homework Statement Why is the difference in electric potential between points A and B defined as the NEGATIVE of the work done in moving a test charge along the path from A to B and then dividing by the charge q? Why the negative sign? Just wondering. Homework Equations Delta V = -...

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...

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.

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...

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...

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...

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...

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...

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

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

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})...

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...

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.