Strange Definition and 566 Threads

integral of (sinx)^2 / (x^2) from -infinity to infinity. how to tackle this

I took this picture at my window sill This orchid plant normally produces flowers with all white petals, like the flower in the back. However this one is clearly deviating with those green marks. Is that normal or strange? Anybody who can shed some light on this?

Hello. I need an explanation for a strange phenomenon ... I use a fan (PC type) powered by mains (220 V / 50 Hz in my country). At a distance of about 3', I get a sin EM field (sure it is not by mains cords) at a stable frequency of 200 Hz synchronized on main frequency. Even during power on...

Hello all, I am trying to learn fortran 90 by rewriting some simple MATLAB codes I have in fortran. I tried to rewrite a linear, 1D finite element code for an elliptic equation and my fortran and MATLAB codes both end up assembling the same system matrixes (K and f), but the solution to...

Can anyone explain the meaning of strange and non strange current.i'm confused about the definition

Homework Statement Find sequence (a_n) s.t. \lim_{N\rightarrow \infty} \sum_{n=1}^{2N} a_n and \lim_{N\rightarrow \infty} \sum_{n=1}^{2N+1} a_n both converge but \sum_{n=1}^{\infty} a_n diverges. I have no idea where to start to be honest. I'm confused at how this is possible. Isn't it always...

I'm given these functions: f(x,y)=x^{3}y ye^{y}=t x^{3}+tx=8 I need to find (df/dt)(0) I have no clue how to go about this. I can't isolate any of the variables. I tried making an implicit function out of equations two and three, but that didn't lead anywhere useful. I'm stumped.

strange laptop smoke :( Ive got an acer aspire 5536 laptop never had a problem with it, a couple of days ago my partner turned the laptop on and saw smoke coming from where the charger was plugged in so she unplugged it turned it off and shouted me, so i plug the charger back in and the power...

Homework Statement The question in it's complete wording: Consider the following curve. y = 8 + 5x2 - 2x3. Find the slope of the tangent to the curve at the point where x = a.Homework Equations (y2-y1)/(x2-x1) where x2=x1+dx and the limit of dx is approaching zero and y2=f(x+dx). The...

I've always noticed something strange about new york city subways. When they start to slow down, you feel a force pushing you forward, which seems fine. However, the subway car actually stops, you feel a jerk backward at that moment. Is there an explanation for this?

Homework Statement ydx - 4(x + y^6)dy = 0 Homework Equations Need to get into the form of dy/dx + f(x)y = G(x) (Standard Form) The Attempt at a Solution ydx = 4(x + y^6)dy y = 4(x + y^6) dy/dx y/4(x + y^6) = dy/dx then I don't know how to get it in the Standard form...

Hi, I'm reading an article where an integral of the form: \int^{\infty}_{-\infty}\,\mathrm{d}\tau' \int^{\infty}_{-\infty}\,\mathrm{d}\tau''... The author then splits this into the region whereby \tau' >\tau'' , and the region \tau''>\tau' ...

Homework Statement A block of mass m slides down a plane inclined at an angle theta with initial velocity v down the slope and with friction coefficient mu. Find T, the time in which the block comes to a rest due to friction. Use coordinates with y vertical and x horizontal. Homework Equations...

Suppose we are looking from an inertial frame at two events in a region of space-time. The first event A (0,0,0,0) is the orign of our frame. The second event is B(10,10,5,15/c) where the 4th corrordinate is time and c is the speed of light. Then the total interval between the to event is ...

Homework Statement Hi guys. I'm really struggling with this problem. Any help is welcomed. Suppose I have a function f(y) = \intg(x)/(x^2) on the set [(y/2)^(1/2), \infty]. g(x) is known to be integrable over all of R. I want to show that f is integrable over [0,\infty], and that the...

hello everyone i am a maintenance engineer in old factory so while we were working on an old machine yesterday we found a very strange gear box like the harmonic drives but it transmitts the motion from the motor shaft by a key to bearings those bearings transmitts motion to a elliptic shaped...

QED: the strange theory of light and matter. " Light is made of particles " ? Over Christmas I ordered the book: QED: The strange theory of light and matter by Richard P feynamn 2006 edition. Note: This book was written in 1985. "We know that light is made of particles because we can't...

Howdy! Question - What is the value of the continued fraction: 1 + 1/(2 + 1/(3 + 1/(4 + ... The continued fraction can also be written: [1; 2,3,4,...] Is there a general method for solving continued fractions with patterns like this? I tried using the recursive formula for the nth...

Dear all, I am taking 'field theory' course this semster and I am reading 'quantum field theory' by mandl and shaw. In chapter 8, equation (8.9) we see: E_1 E_2 v_rel=〖[(p_1 p_2 )^2-m_1^2 m_2^2]〗^(1/2) and we know that as p is a four vector: p=(E,P)=m so p_1 p_2 = m_1 m_2 ! Isn't...

Just to let you know, this is for something I am writing. Well, its not the main topic, just a little something I wanted to expand on. Is there any known drugs/vitamins/supplements that people take to increase their "Brain power" ? By brain power, I just mean anything from increasing...

Can anybody explain how this inverted icicle could have come to be formed ? This mug of water had been sitting outside for a few days, last night the temperature in Edinburgh dropped to below zero, and this morning I saw that this ice stalagmite had formed. There was no source of dripping...

First, a short story to illustrate a philosophical issue I have not seen discussed let alone resolved: Mac was about to press the 'On' button of his super-duper special microwave oven with perfectly reflecting interior walls. Inside, a random jumble of thermal photons, comprising a 'photon...

Strange question, but is "time" and actual "thing"? I was thinking about this today in my Physics class. Is "time" an actual "thing" ? Or just the movement of the hands on a clock? Please give me your opinion (: -Mally

Homework Statement {\int}{\int}{\int}ydV over the region E, where E is bounded by x=0, y=0, z=0, and 2x+2y+z=4 Homework Equations n/a The Attempt at a Solution Assuming that x and y must both be positive, which the boundary conditions seem to require, then the most either one can...

Originally, it is derived from the weight of a confuguration,i.e. how electrons are distributied in different energy level:n=gexp(a+be) It gives the number of electrons in each energy level.However suddenly it can be apply to a cloud of gas?? By dividing a box of gas into different energy and...

Homework Statement Calculate the area under the curve for the following: f(x) = √x*√(−32 − x) and g(x) = √(−x2 − 32x) Homework Equations The Attempt at a Solution I've been trying to do partial integration since the functions f(x)=g(x)area are mirrored, so they are equal...

Homework Statement The integers 1 thru 40 are painted on the outside rim of a circular disk, in “random” order. Prove that some consecutive set of three integers must have a sum that is greater than 61. Hint: this question is not about induction, but about summations of...

Homework Statement We conducted an experiment on the bending of X-Rays in crystals and determined the K_{\alpha},K_{\beta} lines of the first order and the corresponding wavelenghts of the radiation by means of the Bragg equation. We used a NaCl crystal with a d=283 pm. We determined the error...

Homework Statement how come that 16/64=.25 166/664=.25 1666/6664=.25 and any 1then n number of sixes / the same number of sixes then 4 = .25 same thing with 19 / 95 is there other strange division patterns?

Strange Optics Question: photon capture and reproduction Imagine that you are sitting in your room staring out your window at a tree branch and a single leaf about to blow off. Suddenly someone comes up to you and says "You know that window, that's no ordinary window, it is actually a black...

This ad hoping to unseat a judge from the Iowa Supreme Court has to be the early #1 in bizarre campaing ads. https://www.youtube.com/watch?v=Mj2gOLUw5yk

Homework Statement ~ Homework Equations product of permutation The Attempt at a Solution i have difficulty understanding this q. why in \sigma there are b1b2...bn new element? why can i insert \tau in the permutation "matrix"?\tauitself is a "matrix"??

Hi guys, I just wrote a simple code for delta function and print it out. Here it is. program main implicit none integer i real*8 del real*8,parameter:: ep=1D-2 real*8,parameter:: pi=3.1415926 do i=-10,10,1 write(*,*)...

Hello, I just watched at a strange phenomenon. One of my PCB's (Cmos+TTL) is connected to my PC through a Centronics port. No power supply is provided by this wire (only data in and stobe signals). With main power supply off and filtering caps empty, this board runs perfectly during hours and...

This entry on the voice "SUN" in wikipedia is correct? How can this can be possible? And if this entry is true how can be possible to create a small fusion reactor on the Earth? the entry is: The energy production per unit time (power) produced by fusion in the core varies with distance from...

Hi everybody f(x) = aX0 is the form of any constant polynomial... right?? eg: f(x) = 3 is actually f(x) =3X0 where X belongs to R... ok?? since 00 is an unspecified quantity.. therefore on graphing a constant.. it should exists a hole on y-axis... and the y-intercept should not satisfy...

I hope you guys can give me some insight into this situation. So, I was driving home from my parents' house tonight (just past midnight on Monday night) and I'm nearly the only person on the highway. A two state troopers pass me one by one within a 2 minute (2 mile, traveling 60 mph) span...

Homework Statement I am getting fooled by the this improper integral \int_0^{\infty}\frac{cos(x)+sin(x)}{1+v^2}dv = \pi \cdot e^{-x} How the devil do I go about getting that result? The Attempt at a Solution I end up getting the sum of the two integrals...

Two books, same title, same subject, same author. Two radically different prices: https://www.amazon.com/dp/0764574086/?tag=pfamazon01-20 https://www.amazon.com/dp/0764554964/?tag=pfamazon01-20 The new edition is 16 pages shorter. What are the odds of a book being shortened by...

My wife and I are currently staying in a holiday apartment in France and a couple of days ago we think we started seeing the same white flashes in our baby's room at night. We know there's no possibility of external light sources as our baby's room is completely blacked out at night with...

I observed something odd this evening. When I inverted my ball point pen (writing side upwards-perpendicular to the ground level), there was no change in the level of ink. To my surprise, the ink started coming downwards (towards the open end of the refill) when I wrote with it ( inverted ) on...

Homework Statement A particle of mass 1[kg] is moving with a velocity of: \vec{V}=2 \hat{x}+ \hat{y} -4 \hat{z} [m/s] . At the instant t=0, the particle experiences a force which is given by: \vec{F}= \vec{A} \times \vec{V} - (\vec{A} \cdot \vec{V}) \hat {A} where \vec{A}= \hat{x} -6...

The equation of linear thermal expansion is l=l_0\left[1 + \alpha(t - t_0)\right] (it is similar also to the equation of resistivity, \rho=\rho_0\left[1 + \alpha(t - t_0)\right]) \alpha is a constant dependent only on the material we are speaking about. Now, let's say I have a bar 100 m long...

The following question, although probably sounding inappropriate for this forum, is actually very important to me. The easy answer to the question is, “It can’t be done.” But a great deal of learning and increased understanding could be gained if the answer were, “It could be done if...”...

Surge Protector -- strange reaction to light sources? We have 2 power strips in our home in which the indicator lights both react to a light source in the following manner: during the day (in the presence of sunlight) the indicator lights shine red with a small flicker every now and then. In...

how this function f(x)= 0^{-x} should be understood? , if x is NEGATIVE, we find no problems, since 0 raised to any power is 0 but how about x being a positive real number ? , or x being a PURE COMPLEX or complex number ? could we consider a 'regularization' to this f(x) so...

Homework Statement I'm trying to compute something of the form \langle \int_a^b{f(x) dx} \int_a^b{f(x)^{\dagger}dx} \rangle where the dagger means complex conjugate and the brackets are ensemble average (f(x) is a statistical quantity). I'm supposed to use the relation that \langle f(x)...

Homework Statement lim(x→∞)(lnx)^2/x Homework Equations The Attempt at a Solution Since lim(x→∞)(lnx )^2=∞ and lim(x→∞)x=∞, the function is indeterminate, ∞/∞. lim(x→∞)(lnx)^2/x=lim(x→∞) d/dx (lnx )^2/(d/dx x)=lim(x→∞)(2 lnx (1/x))/1 An I am stuck...

My stereo remote has begun exhibiting strange behaviour. If I use the Power button to turn it on (or off), it will continue to do so for as much as 30 seconds. i.e.: - I point the remote at the stereo and press Power, stereo turns on (the on/off cycle on my stereo takes a good 4-5 seconds)...

Homework Statement a ball of 2kg falls from rest froma 5m height and collides elastically with the floor below. what is the magnitude change in the object's momentum? Homework Equations The Attempt at a Solution I did S=So+.5aT^2 I solved for the time it takes to reach the...