Variable Definition and 1000 Threads

Homework Statement How to find the work done by a variable force in (two dimension) When F = ax^2 i + b y^3 j If a subject move from (x1,y1) to (x2, y2) Homework Equations F = dW/dr The Attempt at a Solution I tried to solve them separately by x-direction and y-direction, and then I added...

This is the troublesome part eLeftOutFile = 'data/ElonL'//fileNameSuffix(0:25)//'.dat' OPEN(754,FILE=eLeftOutFile,STATUS='REPLACE',ACCESS='SEQUENTIAL') First off, fileNameSuffix is a CHARACTER(len=40) just to be safe, I am just cutting it off, since those are the relevant parameters...

$(1-x^2)y'' - xy' + 4y =2 x \sqrt{1-x^2} $ Hint use the substitution $x =\sin t$ I used it and end with $\cos t y'' + \sin t y' - \frac{\sin t}{\cos t} y' + 4y = 2\sin t |\cos t| $ how to solve this i just want the name of the method

changing part of a name of a variable in a "for" loop hello everyone! let's say i have the equation between two variables: DT10sec= A*T10sec, working in matlab. How can i use a "for" loop to calculate the equation DT20sec= A*T20sec DT30sec= A*T30sec, DT40sec= A*T40sec,... etc How can i...

Homework Statement We'll be running a vsd water pump. We'll be seeing the energy savings of using a vsd, instead of using an AC motor on full load and using a tap to reduce water flow. Sorry for the lack of info. The Attempt at a Solution I'm sure it will have something to do with...

A problem in this book asks for the most probable value of a random variable x. As far as I know, if a random variable has "most probable value" then it isn't a random variable. The problem is attached. It is the second question in part b. Could the answer be that there is no most probable...

Homework Statement Im supposed to calculate the value of x for 20*log10(\frac{\sqrt{x^2 +1}}{cos(x)}) = 3 The Attempt at a Solution I start off by dividing by 20 on both sides so I just have the expression with log.. and my idea henceforth is to take the inverse of cosine to...

Homework Statement In this exercice I'm asked to find out if the limif of the function f(x,y) exists. lim [SIZE="1"](x,y)→(0,0) sqrt(x*y) / (x^2 - y^2) Homework Equations The Attempt at a Solution I've tried to approach it from different coordinates (y=x, y=0, x=0...

Homework Statement Hi. I'm trying to solve the limit of the function: lim [SIZE="1"](x,y)→(0,0)f(x,y) = = lim [SUB][SIZE="1"](x,y)→(0,0) 3 * x2 / (x2 + y2) Homework Equations The Attempt at a Solution x2 / (x2 + y2) is a limited function. Its image is always between 0 and...

Homework Statement I have some code and I use getchar to read in some input from the user say a5 I have assigned char letter; int number; letter = getchar(); number = getchar(); so that putchar(letter) prints a and putchar(number) prints 5 but when I try ...

I am trying to write code so a 2-d array is written to the hard drive (which is later to be read). There are several do loop iterations and I would like the file name to change with every iteration so I get as many files as there are loop iterations. I get one 1-d array that is named A, no...

Homework Statement The problem initially was a Lagrange multipliers question, and I'm trying to solve for λ. I have an equation in terms of λ alone, but I just can't solve it. I plugged it into Wolfram Alpha and it gave me the λ value in the back of the textbook, but I still don't know how to...

1. how do i solve X'(t)=A(t)X(t) Homework Equations I know of this equation: x(t) = x_0 \exp\left( \int_{t_0}^t f(\xi) \, d\xi \right) but i think that I'm using it wrong. The Attempt at a Solution i have the following mathematica code: A= x = MatrixExp[Integrate[A, {t, 0, s}]].{1, 0,0,0}...

What is the formula to evaluate a multi-integral by a change of coordinates using the squareroot of the metric instead of the determinate of the Jacobian? Thanks.

i have this question i do find the distribution like this figure : and i plot the y like this: now i want to find the distribution of y i tried to take the distribution for each interval in Fx(x) like this : but the solution in the book said : who is wrong me or the book...

If a railroad car traveling down a straight, frictionless track encounters vertical rain that fills it with additional mass, will the velocity decrease in order for the momentum to be conserved? Will the opposite happen if the water is let out from a hole in the bottom? I cannot see any...

Hi all, I have attached my text file(tab delimited). I am planning to read those dataset into real array of (30,38). The dataset has variable decimal places like 312.66, 0, 535.696 ,456122.758. With the following codes, READ(12,*)((X(I,J),I=1,30),J=1,38)...

Homework Statement A player of a video game is confronted with a series of opponents and has an 80% probability of defeating each one. Success with any opponent is independent of previous encounters. The player continues to contest opponents until defeated. What is the probability...

I'm trying to create a variable inductance in SPICE, specifically in NI Multisim. What I'm trying to do is create a saturable inductor. I need an inductor that changes it's inductance with current. Multisim does have a "virtual" inductor that you can create a inductance function with but I can't...

Hi all, I am really confused about the random variables Toss a coin three times, so the set of possible outcomes is Ω={HHH, HHT, HTH, HTT, THH, THT, TTH, TTT} Define the random variables X = Total number of heads, Y = Total number of tails In symbol, X(HHH)=3...

Hi there, I am currently reading Rohatgi's book "An introduction to probabilty and statistics" (http://books.google.de/books?id=IMbVyKoZRh8C&lpg=PP1&hl=de&pg=PA62#v=onepage&q&f=true). My questions concerns the "technique" of finding the PDF of a transformed random varibale Y by a function...

Homework Statement Let X be a continuous random variable with parameters \langle x \rangle and \sigma. Calculate the probability density of the variable Y=exp(X). Calculate the mean and the variance of Y. Homework Equations Reichl's 2nd edition book page 180: P_Y(y)=\sum...

Homework Statement While I was learning about drag and lift on airfloils, I imagined a special airfoil which is fixed at a certain elevation and cannot move vertically (y axis) but can be rotated around its axis (z). Let's assume the direction of the flow to be the x axis. I try to predict...

Homework Statement Homework Equations Only ones I know that are relevant are the equations shown in the question (for the left and right limits). The Attempt at a Solution The difficulty that I am having right not is comprehending what is really being asked from the question. From...

Hey guys, I have a quick question. Suppose X is a chi squared random variable with n degrees of freedom and Y is another independent chi squared random variable with n degrees of freedom. Is X/Y ~ 1 ? Intuitively, it makes sense to me but I'm not too sure.

Homework Statement I must calculate the characteristic function as well as the first moments and cumulants of the continuous random variable f_X (x)=\frac{1}{\pi } \frac{c}{x^2+c^2} which is basically a kind of Lorentzian.Homework Equations The characteristic function is simply a Fourier...

Homework Statement Find and characterise the stationary points for F(x,y,z) = x2 + xy + y2 - 2z2 +3x -2y +z The Attempt at a Solution I found fx, fy, fz and let them equal to 0. Solving gives me the critical point (-8/3,7/3,14). From here I'm not sure how to determine the nature...

Homework Statement 1.21 Express in cylindrical components: (a) the vector from C(3, 2,−7) to D(−1, −4, 2); (b) a unit vector at D directed toward C; (c) a unit vector at D directed toward the origin. I just want to know (a). And the solution from the book is attached, too...

for the given circuit and waveform , i am not getting how output for ωt < π is Vs + E1 ? given Vs is input and equal to Vm Sinωt

Homework Statement I have the ODE y' = f(\frac{y}{x}) , and I want to re-write this as a separable equation using the change of variable u = \frac{y}{x} The Attempt at a Solution I use the chain rule to write y' = \frac{dy}{dx} = \frac{dy}{du}\frac{du}{dx} = \frac{dy}{du}(-\frac{y}{x^2})...

Homework Statement Find k so that the following function is continuous on any interval. j(x) = {k cos(x), x ≤ 0 {10ex − k, 0 < x Homework Equations The Attempt at a Solution I originally thought i had to check if the limits of both parts of the functions...

Hello, I know the value of a field variable in a 3d mapped finite element mesh. Can anyone suggest an effective method/methods to find its gradient throughout the mesh.

I ask this question only to those who read or have this book: If you have Baby Rudin, it would be even better. On the page 34 of the text Conway's Functions of One Complex Variable Vol 1, it proves the Chain Rule but it seems the proof is not valid: It uses sequences to show the limit is...

solve the following equation for z in terms of x and y 3y^{2}+2yz-5z-2x=0 i've spent a lot of time on this question, but i keep getting something along the lines of 0=0 i tried solving for x in temrs of y and z to replace the x but i get 0=0 Homework Statement Homework Equations The Attempt at...

Homework Statement Let f(x)=x/8 be the density of X on [0,4], zero elsewhere. a) Show that f(x) is a valid density and compute E(X) b) Define Y=1/X. Calculate E(Y) c) Determine the density function for Y The Attempt at a Solution a) is just really basic. I've solved that one. b)...

As the title alludes to, I am currently reading about work. One sentence has left me very confused, thought: " Only the magnitude of this variable force changes, not its direction, and the magnitude at any position does not change with time." Could someone possibly help me understand this?

From what I think I understand, a variable is something you input into a function and you get a certain value from it whereas a parameter is something that gives you a different function but 'adjusted'...so the constant C the translates a graph of a function up and down would be a parameter...is...

I just started programming and i don't understand how variables work. First the book defines a as 3 and b as 5 then defines a =a+b. For me who hasnt done programming ever that implies that b=0 but i think second a is different from the first one. Help regarding how variables work in computer

Homework Statement An object starts from position X = 0 and moves along a straight line with its position given by x = 4t^2 - t^3 where t is the time taken to reach position x. Find: i) The time at which the velocity is zero ii) The time at which the acceleration is zero iii) The average...

I have a differential expression that I want to expand to some order around infinity (it's for calculating weak-field limits in GR). I have two functions, B(r) and n(r), and some expression involving them along the lines of n[r] (3 r B'[r]^2 - 4 B[r] (2 B'[r] + r B''[r])) Basically I want...

For my work, I need to solve the following equation for the variable x (if possible): a * (x/1000) = b - x * c Can someone please help me solve it or inform me that it is simply not possible. I'm chemist myself, so solving equations is not exactly my expertise. Thanks in advance!

An object starts from position X = 0 and moves along a straight line with its position given by; X = 20t - 5t^3 where t is the time taken to reach position X. Find; i) The time at which the velocity is zero ii) The time at which the acceleration is zero iii) The average velocity over the...

Homework Statement You run a small business making widgets. You have two employees. Employee A takes two times as long as employee B to make a widget. During each day, both employees working together will make 15 widgets, how many widgets get made by employee A each day? Homework Equations...

The Dirac delta "function" is often given as : δ(x) = ∞ | x = 0 δ(x) = 0 | x \neq 0 and ∫δ(x)f(x)dx = f(0). What about δ(cx)? By u=cx substitution into above integral is, ∫δ(cx)f(x)dx = ∫δ(u)f(u/c)du = 1/c f(0). But intuitively, the graph of δ(cx) is the same as the graph of...

Homework Statement Firstly sorry if this is in the wrong place. I have never submitted a question on this forum about a comp sci question. I got an assignment that asked me to solve for a variable using Bisection of successive approximations. This however is not why I am here as I know you...

I was just wondering if it is possible to find b in this equation? f(x,y)=result. where y=f(a,b). so the I guess f(x,f(a,b))=result. I know the actual value of x,a and result and it is possible to find b in the equation. I also know the function of f(). Please ask me if this...

Homework Statement I'm working through Mahajan's Street-fighting Mathematics for fun, and am a bit puzzled about the following problem: The Attempt at a Solution It's mostly the first part that's tripping me up. I could use the substitution tan\theta=x and solve both integrals...

Hi everybody, I try to figure out connections and differences between random variables (RV), random processes (RP), and sample spaces and have confusions on some ideas you may want to help me. All sources I searched says that RP assigns each element of a sample space to a time function. I want...

The Question: Find the value of r such that v = xr is a solution of xd2v/dx2 + (x+4)\frac{dv}{dx} + 3v = 0 My Solution: After finding the 1st and 2nd derivative of v and substituting into the equation to equat to zero and look for r, I get the answer r =-3. I also get a root that is...

Homework Statement The changing variable formula in partial derivative f(u,v) x=x(u,v) y=y(u,v) (∂f/∂x)y = (∂f/∂u)v(∂u/∂x)y + (∂f/∂v)u(∂v/∂x)y I khow the how chain rule works, but I don't know why in the (∂f/∂u) v is constant and in the (∂u/∂x) y is constant Homework Equations The...