Argument Definition and 375 Threads

VectorPlot[{D[x[t], t] == x[t] (4 - y[t] - x[t]^2), D[y[t], t] == y[t] (-1 + x[t])}, {x, -10, 10}, {y, -10, 10}, {t, -10, 10}] I'm trying to graph the phase plane of these equations. I get an error, what's wrong with my command?

This is an excerpt from a manuscript by William James Sidis published in 1920 called "The Animate and the Inanimate": [SIZE="3"] But there is one outstanding objection to this theory that the stellar universe is infinite. There may be supposed to be no reason why the average...

Homework Statement Is mathematical induction a deductive or inductive argument? Would appreciate the help. Thanks. Jeremy Homework Equations The Attempt at a Solution Its name suggests that the process is inductive, yet I know all of mathematics depends on deductive reasoning...

A Lorentz boost along the x-axis conserves area in the x-t plane. Can anyone think of an argument to prove this fact that's simpler than the one below? I don't want to assume the form of the Lorentz transformation, because I want to use the conservation of area as part of a derivation of the...

There is a logical argument I'd like to have some comments on. I read it in a book, and I am not sure about it. "An instructor teaches a class five days a week, Monday through Friday. She tells her class that she will give one more quiz during the final week of classes, but that the students...

The situation is this: A truck is moving at 70mph with a ramp leading into it at the back. A car with front-wheel drive is behind it doing 75mph. The car goes up the ramp and into the truck. Here is where the dispute starts. My theory: Once the front wheels of the car are on the ramp the...

My friend and I disagree on this problem: A spaceship of proper length 200m moves with respect to us at 0.6c. There are two clocks on the ship, at the bow and stern, that have been synchronized with each other in their rest frame. We, also have a number of clocks synchronized in our frame...

I had a physics test last week. When I got the results, there were some correction mistakes in my opinion, so now it's being revised. I had a small disagreement with my professor over one of the theoric exercises, and tomorrow i'll probably be having the same argument again, so I thought of...

There is an argument to account for the Casimir effect based on cardinalities: that inside the two plates only (virtual) photons with wavelengths corresponding to the harmonic series can exist, hence countable infinity, whereas photons of all wavelengths can exist in the space around it, hence...

Homework Statement Objects are composed of atoms. Atoms are nucleii surrounded by electrons. The electrons are tiny in comparison to the gaps between each other, and between electrons and the nucleus. This means that there are significant gaps between atoms in objects. Homework Equations...

This is pretty much like the twin paradox question: if person A and person B were moving with a velocity v relative to each other and away from each other, then person B would observe a time dilation in person A's reference frame while person A would observe a time dilation in person B's...

Hi, Want to show: a<=r However I ended up with such an argument: For each eps>0, a<r+eps. Does this statement imply a<=r?

-1-(under root)3 i here we find that r=2(hypotenuse) a=-1(base) b=-(under root)3 when i take sin theat= p/h=-(under root)3 / 2 theat from sin is -60 when i take cos theta = b/h =-1 / 2 which gives 120 now one is -60 and other is 120, which is the angel , i have to follow and what...

I've watched the Dateline NBC episode on Vincent Brothers, and was disturbed that the evidence used to convict him was exactly the kind that UFO crackpots like to use. Here's a pretty good summary of the show, even though it's from an unreliable-looking website...

Homework Statement Give an argument for there being a connection between scale length and frequency Homework Equations scale length = (wave length) / (Length)The Attempt at a Solution So from only my physical intuition I'm coming up with the longer the scale length the longer the wave length...

Hello, a couple decades ago, an argument was introduced in a notable physics journal of some kind, but I cannot recall the name of this argument, or the journal. I believe it might have been associated with Cambridge, but can't remember. The argument is a logical theory as to why the...

I just need to make sure that I've got this analysis right: The argument S = 1 - 1 + 1 - 1 + 1 - ... then S = (1 - 1) + (1 -1) + (1 -1) + ... = 0 is invalid because it ignores all sum Sn for n not congruent modulo 2 (not even). The argument S = 1 - 1 + 1 - 1 + 1 - ... then S = 1 - (1 -1) - (1...

can we really give a definition of \delta (x-a-ib) a,b real and 'i' means the square root of -1 if i try it in the sense of generalized function for any x a and b i get the result oo unless b is zero

the question is if we suppose that a function f(n) can take only two values +1 and -1 both with equal probability and define the summatory \sum_{n=0}^{x}f(n) =A(x) how can one prove that A(x)= O(x^{1/2+e}) ?? if we set A(n)=M(n) the Mertens function and since...

Homework Statement Evaluate (1/2ipi)* contour integral of [z^(n-1)] / [(3z^n) - 1 ] dz Homework Equations I would assume you would have to use the Argument Theorem since this problem comes after the proof of the argument theorem in my book. The Attempt at a Solution z^(n-1)...

According to Caratheodory, the first law of thermodynamics (dE=dQ-dW) could be derived from the definition of heat (dQ=dE-dW), whether this form a circular argument or tautology ? How to clarify the confusion between the first law of thermodynamics and the definition of heat，and capture the true...

I was in a discussion with a man. I've read a study about reading habits. The study shows a low average of read books for some countries and told to a man "most of people doesn't read books" because the average was 6 books a year for a sample taken from a population of 100 millions of people...

Hi everyone, I have a couple questions that have been gnawing at my head for some time: Why is it that on wikipedia for the example logarithms and residue at infinity, (on the methods of conour integration link) that the integral is not zero? there are no isolated singularities inside the...

i was wondering whether it was possible to have a class say Vec4(i,j,,k,n) and then being able to assign it as an int eg/ Vec4 A(i,j,k,1) = 1; does this make any sense?

I am confused with the coordinates when using the symmetry argument for this graph. Is Mx=0 using the symmetry argument ?

sorry for starting yet another one of these threads :p As far as I know, cantor's diagonal argument merely says- if you have a list of n real numbers, then you can always find a real number not belonging to the list. But this just means that you can't set up a 1-1 between the reals, and...

It's an old joke, and an old sketch, but some here may not have seen it before, and you can imagine this is how many forum debates end up: http://www.youtube.com/watch?v=teMlv3ripSM&fmt=22

Homework Statement Suppose that a sequence {p}->p, and {q}->q. Show that if p_n < q_n for infinitely many n, then p<q. Homework Equations The Attempt at a Solution I'm sure I know why this is true intuitively. The convergence guarantees that all but a finite number of p_n are within some...

What allows us to do the construction found in Cantor's diagonal argument? Is there an axiom we must adopt to allow for such infinite constructions?

PHP - "Wrong datatype for second argument" So I build this class in my library file (assume that I have all the PHP tags and stuff)... class errorchecker { var $error; function errorsearch($error) { if (in_array($error, $pb)){ echo '<div class="error">'.$error.'</div>'; } }...

Homework Statement Find the modulus and argument of z=1-cos(a)-i*sin(a) Homework Equations mod(z)=sqrt(a^2+b^2) The Attempt at a Solution mod(z)=sqrt((1-cos(a))^2+(-sin(a))^2) =sqrt(2-2cos(a)) arg(z)=arctan((-sin(a))/(1-cos(a))) This is as far as I can get, I have asked my math...

Hey, in my Schaum' Outline Calculus it says Dx(ex) = ex Let y = ex. Then ln(y) = x. By implicit differentiation, \frac{1}{y}y' = 1 therefor y' = y = exFor a more rigorous argument, let f(x) = ln(x) and f-1(y) = ey. Note that f'(x) = \frac{1}{x}. By Theorem 10.2(b). (f-1)'(y) =...

Hello. I am having an argument with two of my friends. They went to Harvard and MIT and are making fun of me for saying you would experience weightlessness in a free falling elevator. They say you would be stuck to the ground and unable to lift your legs since the faster you fall the harder...

Homework Statement By a combinatorial argument, prove that for r \leq n and r \leq m, (^{n+m}_{r}) = (^{m}_{0})(^{n}_{r}) + (^{m}_{1})(^{n}_{r-1}) + ... + (^{m}_{r})(^{n}_{0}) Homework Equations The Attempt at a Solution I need some direction on how to start this problem. It is...

Homework Statement Hi all. When finding the argument of a complex number using tan(\theta) = y/x (where z = x + iy), sometimes I do not get the correct answer. I assume this is because tangent is only defined for -pi/2 to pi/2 (and from this it is periodic). So is it a good idea always...

Given a lagrangian L[\phi], where \phi is a generic label for all the fields of the system, a transformation \phi(x) \rightarrow \phi(x) + \epsilon \delta \phi(x) that leaves the lagrangian invariant corresponds to a conserved current by the following argument. If we were to send \phi(x)...

If z is a complex number, isn't the derivative of arctan(z) just 1/(1+z^2) ? That's what I would think, but my CAS does not agree with me.

Homework Statement Find the argument of (-2+i)(1+2i). 2. The attempt at a solution z=(-2+i)(1+2i)=-4-3i. I've read on the Internet that I can write z=\rho (\cos \theta +i\sin \theta) where \rho is the modulo of z. I've calculated the modulo of z which is 5. So I have that -4=5\cos \theta...

I had a brief conversation with a professor of mine and he presented, in short an argument against the existence of black holes. I'm sure you've heard it or a variation of it. It goes something like this: An advisor and his student are near a black hole. They are both wearing a watch, the...

We're just learning special relativity in class and my lecturer uses the light clock argument (two moving clocks - one parallel and one perpendicular) to explain length contraction. I didn't quite get one thing about it. My notes say the light beam reflects at different times (i.e. they have...

My daughter and I don't agree on pronunciation of the delicious Thai dish, "phad thai." Is it "pod tie" or "pad tie"?

Could someone please help me understand the Einstein hole argument (as outlined by Norton, see below). In particular the step that says that the second solution within the hole is a valid solution to the generally covariant field equation. I think my understanding of general covariance is at...

I have seen conflicting values for the angle where the Argument of the Perihelion of the Earth or where the Winter Solstice(Dec 21) strikes. This is where the ellipse value of the True Anomaly is zero. The two values are: w=114.20783 @J2000 or w=282.9404*4.70935e-5*d where d is a formula...

Hi I've some trouble understanding (or maybe accepting) Cantor's diagonal argument. When I was young I had no trouble accepting it and it seemed perfectly logical, but after a long hiatus and returning to my original interests, I seem less than convinced (must be some age-related or brain decay...

Ok, I've been taught this stuff in school about the particle/wave duality. And what's been always bugging me is that it doesn't really tell me anything : I want a theory that is cohesive without compromises. SO...I was shown an experiment similar to Young's 2 slit experiment. It has a half...

Homework Statement Our teacher made an unconvincing argument based on this example: If a horizontal force of 15 N were a applied to a 2 kg block, and the work done was 20 J, what distance did the object move? 2. The attempt at a solution Using W=F*d the teacher solved this: 20 J=15 N*x ->...

Homework Statement Our teacher made an unconvincing argument based on this example: If a horizontal force of 15 N were a applied to a 2 kg block, and the work done was 20 J, what distance did the object move? 2. The attempt at a solution Using W=F*d the teacher solved this: 20 J=15 N*x...

I am looking for a chart for each planet. This chart must contain each planet's angle from it's argument of perihelion for a particular time on Earth time. I am not looking for an ephemeris, I don't think. I need the angle along the eliptical path of the planet or the true anomaly.

Not trying to get into any religious debate here, but often an argument from believers is that, without a god, the universe would've had to "come from nothing". The question is, do we have any reason at all to believe that the "natural" state of affairs should be nothing instead of something...

A friend of mine came up with an annoyingly simple argument for a Newtonian, deterministic, causally necessary universe. I can't see how to refute it Based on 2 things- The "Principle Of Least Action" A particular definition of "Event". That's it! "Principle Of Least Action"- The...