Integration Definition and 1000 Threads

  1. thegreengineer

    Integral calculus: integral variable substitution confusion

    Recently I started seeing integral calculus and right now we are covering the topic of the antiderivative. At first sign it was not very difficult, until we started seeing integral variable substitution. The problem starts right here: Let's suppose that we have a function like this: \int...
  2. Calpalned

    Calculating Arc Length for Parametric Equation x = e^t + e^-t and y = 5 - 2t

    Homework Statement The question involves finding the arc length of the parametric equation x = e^t + e^-t and y = 5 - 2t Homework Equations Arc length of a parametric equation ∫√(dy/dt)^2 + (dx/dt)^2 dt limits are from 0<t<3 The Attempt at a Solution Taking the derivative of both x and y...
  3. Calpalned

    Use of integration to find area

    Homework Statement Find the area enclosed by the curve x = t^2 -2t, y = t^0.5 and the y axis Homework Equations Area of a parametric curve = ∫g(t) f'(t) dt, where g(t) = y and f(t) = x The Attempt at a Solution I believe that the limits of integration by be found by setting x and y equal to...
  4. C

    How Do I Match Integrals to the Correct Formulas in Integral Tables?

    I would really appreciate it if people could help with these integrals. We are supposed to be doing integrals with this table here: http://math.boisestate.edu/~wright/courses/m333/IntegralTablesStewart.pdf Here are the two integrals. Technically, I only need one of them completed...
  5. ognik

    Tricky Intregral for numerical quadrature

    Hi - I have just started 'Computational Physics' by Koonin & Meredith, - through distance learning. Exercise 1.3 needs a program to evaluate an integral - I'm finding myself kinda rusty on integrals. The hint says - split range of integration into parts, use different change of variable in each...
  6. A

    Just started Antiderivatives Help?

    Homework Statement F[/B]ind the Antiderivative of: (x^3-1)/(x-1). All is known is the integration formulas (i.e. ∫sinx = -cosx+c) Homework Equations Integration Formulas the most complicated being ∫cscx dx= -ln(cscx+cotx)+c The Attempt at a Solution I tried doing (x^3/x-1) -(1/x-1), but now...
  7. H

    Relationships between integration limits of Maxwell Equation

    I don't understand the relationships between the integration limits of Maxwell Equations (specifically the ones in integral form in matter) Is this related to Stokes/Gauss' Theorems? or something else?
  8. Mr Davis 97

    Defining differentitation and integration on functions

    I have a question concerning how how we define the differentiation and integration operators. Firstly, I know that functions are typically defined as an ordered triple triple ##(X, Y, f)## such that ##f⊆X×Y##, where ##x \in X## and ##f(x) \in Y##. This all seems nice and fine, but we also define...
  9. J

    MHB Integration by Parts for Cosine Squared: Is My Approach Correct?

    Greetings :) Well I wanted to seek help if my solution is on the right path, given as follows: 1) \int cos ^2x dx So my solution follows like this: u = cos^2x du = 1/2 (1+cos(2x)) v = x dv = dx but I've stuck when its in the u.v - \int v.du cos^2 (x) - \int...
  10. S

    Parametric + analytic function integration

    Hello. Let's imagine that we have a parametric function f1(x(t),y(t),z(t)) and an analytic one f2(x,y,z) and we have to integrate their product over some volume dx dy dz. So what are analytical tools for it? Thanks!
  11. A

    Residue of f(z) involving digamma function

    Homework Statement Find the residue of: $$f(z) = \frac{(\psi(-z) + \gamma)}{(z+1)(z+2)^3} \space \text{at} \space z=n$$ Where $n$ is every positive integer because those $n$ are the poles of $f(z)$Homework EquationsThe Attempt at a Solution This is a simple pole, however: $$\lim_{z \to n}...
  12. S

    Can the Volume of Revolution Be Negative?

    There is a nice equation made by Nobuo Yamamoto which describes the curve of an egg and it is: (x^2 + y^2)^2 = ax^3 + (3/10)xy^2, where a is the length of the major axis of the egg. Solve this equation for y, we get: y=+/- sqrt((3/20)ax - x^2 + xsqrt((7/10)ax + (9/400)a^2)) When I rotate the...
  13. B

    Please explain how this integration is done

    Hi Attached is an extract of a paper by Lord Rayleigh on pressure generated during collapse of a bubble in a liquid. Will someone please explain how the RHS of equation (2) in the attachment is obtained ? TIA
  14. A

    MHB Replacing Variables in Integration

    I have asked the same question on math stackexchange under the moniker "anonymous," since I do not wish to be known there. I will try my luck here.$$I = \int_{-\infty}^{\infty} e^{-x^2} dx$$ I don't understand, we say: $$I = \int_{-\infty}^{\infty} e^{-x^2} dx$$ Then we say: $$I =...
  15. A

    Replacing Variables in Integration

    Homework Statement $$I = \int_{-\infty}^{\infty} e^{-x^2} dx$$ Homework Equations Below The Attempt at a Solution $$I = \int_{-\infty}^{\infty} e^{-x^2} dx$$ I don't understand, we say: $$I = \int_{-\infty}^{\infty} e^{-x^2} dx$$ Then we say: $$I = \int_{-\infty}^{\infty} e^{-t^2} dt$$...
  16. electronic engineer

    Integrate f(t) from 0 to 1/n: Explained

    Hello, I passed by this integration and couldn't understand the moving from the left hand to the right hand side. $$ \int_{0}^{1/n}f(t)dt=\frac{1}{n}f(0) $$ could you please tell me why this is??
  17. M

    Integration by Parts: Does the Choice of u and dv Matter?

    Homework Statement $$ \int x^{3}cos(x^{2})dx$$ The attempt at a solution OK, so I am aware that there is a way in which to do this problem where you do a substitution (let $$u=x^{2}$$ to do a substitution before you integrate by parts), and I was able to get the answer right using this method...
  18. L

    Corollary 8: Integration in 'Polar Coordinates'

    I am reading Spivak's Differential Geometry Vol. 1. I am stuck for some days in chapter 8 about integrating forms on manifolds. Maybe someone can clear my doubt. First, I will 'type' what the corollary says: My doubt is regarding this affirmation: The book it says is easy to see. Well...
  19. G

    Jefimenko's Equations: Integrals & Integration

    http://en.wikipedia.org/wiki/Jefimenko's_equations What is the integral in these equations called? how do you integrate over (d^3)r'?
  20. R

    Finding Solutions to a Step Function Integral

    Homework Statement This is from Apostol's Calculus Vol. 1. Exercise 1.15, problem 6.(c) Find all x>0 for which the integral of [t]2 dt from 0 to x = 2(x-1) Homework Equations [t] represents the greatest integer function of t. The Attempt at a Solution [/B] Integral of [t]2 dt from 0 to x...
  21. F

    Help with an intermediate integral

    Homework Statement I have been trying to evaluate an integral that has come up in the process of me solving a different problem, but am completely stuck. As I have confirmed with Wolfram Alpha that the integral once solved yields the correct solution to my problem. However, I am trying to...
  22. A

    Calculating Harmonic Sums using Residues

    I posted the same question on Math Stackexchange: http://math.stackexchange.com/questions/1084724/calculating-harmonic-sums-with-residues/1085248#1085248 The answer there using complex analysis is great. I had questions, which Id like to get advice on here. (1) How did he get the laurent...
  23. A

    MHB Evaluating a rational function with contour integration

    Hello, I am looking to evaluate: $$I = \int_{0}^{1} \frac{x^4(1-x)^4}{1+x^2} dx$$ I will use a rectangular contour. The image looked weird here so the upload of the image is here: http://i.stack.imgur.com/W4BfA.jpg $R$ is more like the radius of the small semi circle, we have to let $R \to...
  24. P

    Arc Length: Definite and Indefinite Integration

    Several authors state the formula for finding the arc length of a curve defined by ##y = f(x)## from ##x=a## to ##x=b## as: $$\int ds = \int_a^b \sqrt{1+(\frac{dy}{dx})^2}dx$$ Isn't this notation technically wrong, since the RHS is a definite integral, and the LHS is an indefinite integral...
  25. J

    Fourier sine series integration

    Homework Statement The question is to get Fourier sine series of e^-x =f(x) on 0<x<1 Homework Equations Bn = 2/L ∫ (e^-x) * sin(nπx/L) over the limits 1 to 0, where L = 1 f(x) = summation of Bn*sin(nπx/L) The Attempt at a Solution So I integrated ∫ by part integration so I took u =...
  26. F

    Convergence of Integral with Real and Imaginary Parameters

    The integral given below is to be computed as a function of real variables x and s. Even a partial answer only for s>0 is very useful. Here is the integral: $$\int_{0}^{\infty}{dk \frac{k^2 e^{-k^2 x^2}}{(k^2 + s)^{3/2}}}$$ Thank you for your help.
  27. A

    MHB Complex Contour Keyhole Integration Methods

    This is an interesting complex analysis problem; **The figure on the bottom left is what is being referred to,Fig7-10.** **Firstly: (1)** How is the branch point $z=0$ at $z=0$?? We have $f(0) = 0$ that is not a discontinuity is it? **Secondly:(2)** It says that: $AB$ and $GH$ are coincident...
  28. QPingy

    Numerical integration - verlet algorithm - accuracy

    In my computational physics textbook, three different velocity estimators are derived for a problem with equation of motion: \ddot x = F(x) where the positions are found by using the Verlet algorithm: x(t+h) = 2 x(t) - x(t-h) + h^2 F[x(t)] The three velocity estimators are: v(t) = \frac{x(t+h)...
  29. A

    MHB Complex Contour integration of rational function

    Hello, Evaluate: $$\int_{0}^{\infty} \frac{\cos(x)}{x^2 + 1} dx$$ We know that because $f(x)$ is even:$$\int_{0}^{\infty} \frac{\cos(x)}{x^2 + 1} dx = \frac{1}{2} \cdot \int_{-\infty}^{\infty} \frac{\cos(x)}{x^2 + 1} dx$$ Consider a complex function, with $z = x + iy$ $$f(z) =...
  30. J

    Exponential integration confused

    Hi, does anyone know how to integrate e^-x (sin(nπx))? I have tried part integration but that goes on until infinity... and I am not sure how to use the substitution method...Please help! I have tried taking e^-x as U but then I end up getting the entire canceled off then...
  31. B

    Which Integral Calculation is Correct?

    Homework Statement Which one is correct? ##\int (3x+2) (2x+1)^{\frac{1}{2}} dx = \frac{1}{3} (3x+2)(2x+1)^{\frac{3}{2}} - \frac{1}{15} (2x+1)^{\frac{5}{2}} + C## or ##\int (3x+2) (2x+1)^{\frac{1}{2}} dx = \frac{1}{3} (3x+2)(2x+1)^{\frac{3}{2}} - \frac{1}{5} (2x+1)^{\frac{5}{2}} + C## ...
  32. J

    Heat equation problem so confusing

    Homework Statement The problem is f(x) = sin2πx - (1/πsquare)*sinπx and its given Bn sin (nπx) = f(x) Question is find Bn. Homework Equations Bn = 2/L ∫ (sin2πx - (1/πsquare)*sinπx) * sin(nπx/L) where L is 1 The Attempt at a Solution I did [/B] ∫ sin2πx * sin (nπx) - (1/πsquare)*sin...
  33. J

    Solve Wave Equation: e^(-x^2), x*e^(-x^2), -infinity<x<infinity

    Homework Statement So it says solve this wave equation : [y][/tt] - 4 [y][/xx] = 0 on the domain -infinity<x<infinity with initial conditions y(x,0) = e^(-x^2), yt(x,0) = x*(e^(-x^2)) Homework Equations I used the D Alembert's solution which is 1/2(f(x+ct)+f(x-ct)) + 1/2c ∫ g(z) dz The...
  34. T

    How Can I Find the PDF Along One Axis for Exponential Decay in 2D Space?

    I'll like to know the probability density function for one of the x or y axis, given that there is an exponential decay of a material in two-dimensional space. So, that means I have to marginalize, say y and keep x, but I couldn't solve the integration. I even tried with Mathematica and Matlab...
  35. V

    Integration constants, gravitational potential of sphere

    Homework Statement So I'm calculating the gravitational potential of a sphere at at point P. R = radius of sphere, r = distance from center of sphere to point P. I'm looking at two scenarios; r > R (1) and r < R (2). So I have the following integral: \begin{equation} V(r) = \int...
  36. Z

    Volume of a Solid Revolved About X-Axis

    I'm trying to practice for my final. The sample problem is: "Find the volume of the solid generated when the region bounded by y = x4and y = x1/3, 0<=x<=1, is revolved about the x-axis." To start, I set the two y equations equal to each to find the points of intersection. x4 = x1/3, : raise...
  37. M

    Checking if Momentum Operator is Hermitian - Integration

    Homework Statement I'm checking to see if the momentum operator is Hermitian. Griffiths has the solution worked out, I'm just not following the integration by parts. Homework Equations int(u dv) = uv - int(v du) The Attempt at a Solution I've attached an image of my work. It seems there...
  38. SalfordPhysics

    Comp Sci Fortran90: DO loop for sequence of numbers

    Homework Statement A program finds the area under the Gaussian Distribution Curve between ±σ using Simpsons Rule. Modify the program to investigate the effect of the number of strips. Do this by using a DO loop in the main program for the following sequence of number of strips (n); n-2, n-4...
  39. B

    Integration of x^{-4}y' - 4x^{-5}y = xe^x: Solution and Explanation

    Homework Statement Solve: ##x \frac{dy}{dx} - 4y = x^6 e^x.## Solution: Dividing by ##x##, we get the standard form ##\frac{dy}{dx} - \frac{4}{x}y = x^5 e^x.## Hence the integrating factor is ##e^{\int -\frac{4}{x}dx}= e^{-4 \int \frac{1}{x}dx} = e^{-4 \ln x} = e^{\ln x^{-4}} = x^{-4}##...
  40. S

    Use of substitution for integration

    I was wondering if there is a convenient way of checking if a substitution is correct or not. For example, I tried solving for ∫(1/(a^2-x^2)dx using two different substitutions, x=acosu and x=asinu giving different solutions. I got the integral as arcsin(x/a) using x=asinu and -arccos(x/a) using...
  41. M

    What is the Equation for Water Pressure on a Dam Wall?

    Homework Statement Consider a simple model of a free-standing dam, depicted in the diagram. Water of density ρ fills a reservoir behind the dam to a height h. Assume the width of the dam (the dimension pointing into the page) is w. (a) Determine an equation for the pressure of the water as...
  42. N

    Integrate x^(5/2) e^(-x): Solving w/ Substitution & √2π

    Homework Statement Using \int_{-\infty}^{\infty}e^{-x^2/2} dx = \sqrt{2\pi}, Integrate x^(5/2) e^(-x) dx from 0 to infinty 2. The attempt at a solution I tried substituting x = u^2/2 but i could not simplify further. Please help me with the problem. Thank you in advance.
  43. little neutrino

    Solving Electric Field of an Insulating Slab

    Homework Statement A slab of insulating material has thickness 2d and is oriented so that its faces are parallel to the yz-plane and given by the planes x = d and x = -d. The y- and z- dimensions of the slab are very large compared to d and may be treated as essentially infinite. Homework...
  44. I

    MHB How Do You Evaluate and Differentiate Complex Trigonometric Functions?

    Evaluate ∫[sin2x/(1+(cos)^2 x) dx]Differentiate f(x) = (sin)^2 (e^((sin^2) x)) Hello, I'm just really stumped with these review questions and i have a test coming up. For the first, I'm not too sure what to do since there is a sin2x in general and for the second i don't know how to deal the...
  45. DivergentSpectrum

    Is the Alternative Method for Integration by Parts Simpler?

    I have a question why everyone says ∫uv' dx=uv-∫u'v dx why don't they replace v' with v and v with ∫vdx and say ∫uv dx=u∫vdx-∫(u'∫vdx) dx i think this form is a lot simpler because you can just plug in and calculate, the other form forces you to think backwards and is unnecessarily complicated.
  46. T

    What Are the Limits of Integration for a Sphere and Cone Intersection?

    Homework Statement sketch the solid region contained within the sphere, x^2+y^2+z^2=16, and outside the cone, z=4-(x^2+y^2)^0.5. b) clearly identifying the limits of integration, (using spherical coordinates) set up the iterated triple integral which would give the volume bounded by the...
  47. B

    Solving Difficult Integrals: Step by Step Guide

    Homework Statement ##(e^y + 1)^2 e^{-y} dx + (e^x + 1)^3 e^{-x} dy = 0## Homework EquationsThe Attempt at a Solution ##(e^y + 1)^2 e^{-y} dx + (e^x + 1)^3 e^{-x} dy = 0## ##(e^{2y} + 2 e^y + 1) e^{-y} dx + (e^{3x} + 3e^{2x} + 3e^x + 1) e^{-x} dy = 0## ##(e^{2y - y} + 2 e^{y - y} + e^{-y}) dx...
  48. gracy

    Integration Constant in Physics: When to Use It?

    I have not taken maths so you may find my question silly. in physics i have to deal with integration.so can you please tell me where we write integration constant and where we don't?
  49. B

    Need help with Schrödinger and some integration

    My wave function: ##\psi_2=N_2 (4y^2-1) e^{-y^2/2}.## Definition of some parts in the wavefunction ##y=x/a##, ##a= \left( \frac{\hbar}{mk} \right)##, ##N_2 = \sqrt{\frac{1}{8a\sqrt{\pi}}}## and x has an arrange from ##\pm 20\cdot 10^{-12}##. Here is my integral: ##<x^2> =...
  50. T

    Integration seems gaussian but the answer does not match

    Homework Statement -h^2/2m (sqrt(2b/pi)) e^(-bx^2) d^2/dx^2 (e^(-bx^2)) dx from - to + infinity Homework Equations I tried differentiating e^(-bx^2) twice and it came up weird , I positioned the values and finally cam up with (-2b sqrt(pi/2b)...is there any other way to do it ? The...
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