Integral Definition and 1000 Threads

  1. Z

    MHB How to calculate this type of integral

    Could anyone can tell me how to calculate this type of intergretion. Thanks very much $$\int\frac{{y}^{3}}{(196 - {y}^{2})\times \sqrt{196 - {y}^{2} - {a + y}^{2}}}$$
  2. D

    Meaning of the FFT of a Poynting Vector integral, reflection coefficient

    Hello, For calculating the mean power at a specific cross section of a waveguide, one can calculate the mean value of the temporal function of Poynting Vector, P(t), where P(t) is the ExHy-EyHx. Note that I am not talking about phasors or a sinusoidal state. If I integrate over the waveguide...
  3. SemM

    Undergrad Can you simplify this integral or do you need more background knowledge?

    Hi, I have the following integral which I am not confident on how to interpret (solve):\begin{equation} \alpha \bigg( \int_0^L [\frac{d^3}{dx^3}\phi] \psi dx - \int_0^L [\frac{d^3}{dx^3}\psi] \phi dx \bigg) \end{equation} at this stage, I am not sure which rule to use to solve each of the two...
  4. J

    Graduate Maximization Problem: Double Int. w/ C not Dependent on Integrals

    Consider a double integral $$K= \int_{-a}^a \int_{-b}^b \frac{B}{r_1(y,z)r_2^2(y,z)} \sin(kr_1+kr_2) \,dy\,dz$$ where $$r_1 =\sqrt{A^2+y^2+z^2}$$ $$r_2=\sqrt{B^2+(C-y)^2+z^2} $$ Now consider a function: $$C = C(a,b,k,A,B)$$ I want to find the function C such that K is maximized. In other...
  5. karush

    MHB 244.T.15.5.11 Evaluate the triple integral

    $tiny{244.T.15.5.11}$ $\textsf{Evaluate the triple integral}\\$ \begin{align*}\displaystyle I_{\tiny{11}}&=\int_{0}^{\pi/6}\int_{0}^{1}\int_{-2}^{3} y\sin{z} \, d\textbf{x} \, d\textbf{y} \, d\textbf{z}\\ &=\int_{0}^{\pi/6}\int_{0}^{1}...
  6. lfdahl

    MHB Integral challenge ∫ln2(1+x^(−1))dx

    Evaluate the definite integral $$\int_{0}^{1} \ln^2(1+x^{-1}) \,dx$$
  7. karush

    MHB What is the value of the triple integral 15.4.08?

    \begin{align*}\displaystyle I_{15.5.8}&=\int_{0}^{\sqrt{2}} \int_{0}^{3y} \int_{x^2+3y^2}^{8-x^2-y^2} dz \ dy \ dx \\ &=\int_{0}^{\sqrt{2}} \int_{0}^{3y} \Biggr|z\Biggr|_{x^2+3y^2}^{8-x^2-y^2}\\ &=\int_{0}^{\sqrt{2}} \int_{0}^{3y} 8-2x^2-4y^2 \ dy \ dx \\ &=\int_{0}^{\sqrt{2}}\Biggr|8y-2x^2...
  8. Eclair_de_XII

    How to interpret the hazard function and its integral?

    Homework Statement "Suppose that the accident rate for one workplace ##A## is ##k## times the rate of another workplace ##B##. In other words, ##\lambda_A(t)=k⋅\lambda_B(t)##. Conclude that the probability of no accidents in workplace ##A## is the probability of no accidents in workplace ##B##...
  9. H

    Find f(x) which satisfies this integral function

    Homework Statement find f(x) which satisfies f(x) = x + ##\frac{1}{\pi}## ##\int_{0}^{\pi} f(t) \sin^2{t} \ d(t)## Homework EquationsThe Attempt at a Solution to solve f(x), I have to solve the integral which contains f(t). And f(t) is the f(x) with variable t? if yes, I will get integral...
  10. Z

    Graduate How can I Prove the following Integral Inequality?

    I want to prove the following inequality: $$\sum\limits_{k\in\mathbb{N}}\Big(\int \big|f(x)\big|\big|g(x-k)\big|dx\Big)^2 \leq \big\|f\big\|^2 \sum\limits_{k\in\mathbb{N}}\Big (\int\big|g(x-k)\big|dx\Big)^2$$ where $$\|f\|^2=\int |f(x)|^2dx.$$ My attempt: Just prove the following inequality...
  11. nightingale123

    Undergrad N-th dimensional Riemann integral

    Hello I have a question regarding something we wrote in class today. Let ##A## be a bounded subset of ##R^n##, let ##f,g:A\to \mathbb{R}## be integrable functions on A. ##a)## if ## A## has a volume and ##\forall x \in A :m\leq f(x) \leq M## then ##mV(A)\leq \int_{A}f(x)\leq MV(A)## this...
  12. pawlo392

    Graduate Convergence of an Integral Involving Lebesgue Measure and Sine Functions

    Hello. I have problem with this integral : \lim_{n \to \infty } \int_{\mathbb{R}^+} \left( 1+ \frac{x}{n} \right) \sin ^n \left( x \right) d\mu_1 where ## \mu_1## is Lebesgue measure.
  13. giokrutoi

    Undergrad Can i find this integral in a simpler way

    ∫x^2/(4x+1)^10 dx i know that solving this is possible by partial fractions like A/4x+1 + (Bx+C)/(4x+1)^2 + (Dx+E)/(4x+1)^3 and so on but i would like to know if there is another way of solving this.
  14. GaussianSurface

    How can I find this displacement?

    Homework Statement Your task is to estimate how far an object traveled during the time interval 0≤t≤8, but you only have the following data about the velocity of the object. *First image You decide to use a left endpoint Riemann sum to estimate the total displacement. So, you pick up a blue...
  15. GaussianSurface

    Calculating distance from speed

    Homework Statement The speed of a runner increased during the first three seconds of a race. Her speed at half-second intervals is given in the table. Find lower and upper estimates for the distance that she traveled during these three seconds. It follows the image's square. Homework Equations...
  16. W

    Writing integrals in terms of the error function

    Homework Statement I have the following integral, $$\frac{1}{\sigma \sqrt{2\pi} t} \int_{-\infty}^{0} \exp[\frac{-1}{2\sigma ^2} (\frac{x-x_0}{t} - p_0)^2]dx$$ that I wish to write in terms of the error function, $$erf(x) = \frac{2}{\sqrt{\pi}} \int_{0}^{x} e^{-g^2}dg$$ However, I can't seem...
  17. J

    Graduate Path Integral of a Spontaneously Broken Theory

    A scalar field theory with potential $$V(\phi)=-\mu^2\phi^2+\lambda \phi^4$$ is spontaneously broken and as a consequence, for the ground state, $$\langle \phi(x) \rangle \neq 0$$. However, the path integral, which should give ground state expectation values, looks to be zero by oddness of the...
  18. J

    Cauchy Integral of Complex Function

    Homework Statement Homework Equations Using Cauchy Integration Formula If function is analytic throughout the contour, then integration = 0. If function is not analytic at point 'a' inside contour, then integration is 2*3.14*i* fn(a) divide by n! f(a) is numerator. The Attempt at a Solution...
  19. J

    What are the dimensions and boundaries for different types of integrals?

    Homework Statement [/B]Homework Equations Substitution. The Attempt at a Solution Since the circle is of unit radius and around origin, limits are x = -1 to 1, and y = -1 to 1 I replaced x by cos t, and y by sin t. But what to put in place of ds? I thought about divergence theorem, but then...
  20. H

    What is the Method for Finding Area Between Curves?

    Homework Statement Homework Equations The Attempt at a Solution I'm confused avout questions 2-3. The answers for 2-2 is 1 So the answer for 2-3 is $$\frac{1}{3}$$ But, how the area looks like? Because $$ x^2 $$ will be an open curve upside? There's no boundary for above side.
  21. DeathbyGreen

    Undergrad Loop Integral Form: Finding a Workable Solution without Regularization

    Hi, I'm trying to calculate an integral which looks unfortunately divergent. The structure is similar to a loop integral but the appendix in the Peskin textbook didn't have a useable form. The integral form is (I did a u substitution to make it easier to look at) \int_x^{\infty}du...
  22. P

    Calculate the Dirac delta function integral

    https://1drv.ms/w/s!Aip12L2Kz8zghV6Cnr8jPcRTpqTX https://1drv.ms/w/s!Aip12L2Kz8zghV6Cnr8jPcRTpqTX My question is in the above link
  23. lfdahl

    MHB Evaluate Integral: \(\cos x \cdot \cdot \cdot \cos 2^{2018}x\)

    Evaluate \[\int_{0}^{2\pi}\cos x \cos 2x \cos 4x \cdot \cdot \cos 2^{2017}x \cos (2^{2018}-1)x \: dx\]
  24. V

    Integration with Respect to x: Integral of sqrt((5-x)/x)

    Homework Statement integration with respect to x Homework Equations integral 1/sqrt (a^2 - x^2) = arcsin(x/a) The Attempt at a Solution image attached, the arcsine term in 5/2 arcsin((2x-5)/5) it should be 5 arcsine(sqrt(x/5))
  25. F

    Graduate Can Newton's method work with an approximated integral

    I have a system of equations, and one of them is this : ##\int(1-U(y))Dy - H*\int(U(y)-U(y)^2)dy=0## Can Newtons method work if I approximate this integral to be ##\sum_y(1-U(y))-H\sum(U(y)-U(y)^2)=0## y is a set integers in range ##[1,1000]## I have Newtons method working for this same system...
  26. Pushoam

    What is the line integral of a curve?

    Homework Statement Homework EquationsThe Attempt at a Solution Line integral of a curve ## I = \int_{ }^{ } yz dx + \int_{ }^{ } zx dy + \int_{ }^{ } xy dz ## with proper limits. ## I = \int_{\frac { \pi }4}^{ \frac { 3 \pi} 4} abc ( \cos^2 t - \sin^2 t ) dt = -abc ## |I| = abc...
  27. M

    How to Prove the Integral of sin^7 x/(1+x^10) dx from -pi/2 to pi/2 is 0?

    Homework Statement Find the integral of sin^7 x/(1+x^10) dx from -pi/2 to pi/2. Homework Equations None. The Attempt at a Solution sin^7 x means sinx to the 7th power. But how do I find this strange integral? I don't think u-substitution, trig identity, any of them will work.
  28. M

    Integrating 1/(1+cosx) from -pi/2 to pi/2

    Homework Statement Find the integral of 1/(1+cosx) dx from -pi/2 to pi/2. Homework Equations None. The Attempt at a Solution Here's my work: 1/(1+cosx)=(1-cosx)/((1+cosx)(1-cosx))=(1-cosx)/(1-cos^2 x)=(1-cosx)/sin^2 x This is what I've got so far. But this doesn't seem to simplify the...
  29. B

    Contour integral and problem of Quantum mechanics (Griffiths)

    Homework Statement Homework Equations This is solution of Griffith problem 11.16 The Attempt at a Solution This is procedure to get a 1-D integral form of Schrödinger equation. I don't understand why that contour integral include only one pole for each contour?
  30. S

    High School How to interpret the integral of the absolute value?

    This is rather basic, and may be a misconception of the notation, however, I can't make the following sum up: The following is given: x_n(t) = 1 -nt , (if 0 <= t <= 1/n) and 0, (if 1/n < t <= 1) However, this part I can't grasp this part in the book: \begin{equation} ||x_n||^2 = \int_0^1...
  31. B

    Integral Calculation for Yukawa Potential Differential Cross Section

    Homework Statement Homework Equations This is a calculation about differential cross section of Yukawa potential. The Attempt at a Solution I can't understand how that highlighted part can be -1 , we don't know if the parenthesis term (iq-1/a) is negative or positive tho.
  32. lfdahl

    MHB Definite integral challenge ∫ln(2−2cosx)dx=0

    Prove, that the definite integral $$\int_{0}^{\pi}\ln (2-2\cos x)dx = 0.$$
  33. A

    MHB How Do You Calculate the Radius of Curvature for Complex Curves?

    1) Find the radius of curvature at any point of the cycloid x = a(\theta + sin\theta)y = a(1- cos\theta). 2) Find the radius of curvature at the point (3a/2 , 3a/2) for the curve x3 + y3 = 3axy
  34. J

    MHB Integral of Rational Exponential

    Hi, I'm new to this forum. This semester I took Calculus I and just took the final yesterday. There were a few questions that were unexpected that I didn't know how to handle. This integral has got me stumped.$$\int_{0}^{1} e^{x}/(1 + e^{2x}) \,dx$$ The techniques I know at this point...
  35. F

    Undergrad Problem understanding the shear force integral.

    The problem is to determine the shearforce Q on the hut near the ground. This is not a homework or anything like that, I'm just studying for an exam and this problem is in the book "Engineering Mechanics, Statics" By Meriam Kraige. On another forum, I found this: I understand the part in...
  36. D

    MHB Evaluate Case of Fresnel Integral

    Evaluate $\lim\limits_{{n}\to{\infty}} \int_{n}^{n+1} \cos^2(x^2) \,dx$ I've tried using the half angle identity and the taylor series on the remaining $1/2 + \cos(2x^2)$ to prove the value is $1/2$, but I am out of ideas.
  37. C

    Graduate Why Is the Rayleigh Sommerfeld Integral Challenging to Compute Directly?

    Hi, I have read about the rayleigh sommerfeld integral and its a surface integral. Why is it difficult to calculate the integral directly?
  38. mertcan

    Graduate Collision integral approximation in boltzmann equation

    Hi, as you can see at the end of the picture/attached file collision integral is approximated to a discrete sum. Could you express how this approximation is derived?
  39. S

    Triple Integral of y^2z^2 over a Paraboloid: Polar Coordinates Method

    Homework Statement Evaluate the triple integral y^2z^2dv. Where E is bounded by the paraboloid x=1-y^2-z^2 and the place x=0. Homework Equations x=r^2cos(theta) y=r^2sin(theta) The Attempt at a Solution I understand how to find these three limits, -1 to 1 , -sqrt(1-y^2) to sqrt(1-y^2) , 0 to...
  40. R

    Undergrad Understanding the Constant of Integration in RL Circuit Equations

    I am having problem on understanding the below solution regarding constant of integration. On integrating an differential equation of RL circuit , for e.g $$10i + 3\frac{di}{dt} = 50 $$ $$i.e \frac{di}{50-10i} =\frac{dt}{3}$$ Integrate $$\frac{1}{10} \int\frac{1}{5-i} di = \frac{1}{3}∫dt...
  41. M

    MHB Calculate integral using Stokes Theorem

    Hey! :o I want to calculate $\int_{\sigma}\left (-y^3dx+x^3dy-^3dz\right )$ using the fomula of Stokes, when $\sigma$ is the curve that is defined by the relations $x^2+y^2=1$ and $x+y+z=1$. Is the curve not closed? Because we have an integral of the form $\int_{\sigma}$ and not of the form...
  42. S

    Undergrad Integral of e^(ikx^3): Write as Line Integral from 0 to $\infty$

    Show that $$\int_0^\infty dx\exp(ikx^3) , k>0$$ may be written as integral from 0 to ##\infty## along the line ##arg(z) = \frac{\pi}{6}##. I'd appreciate it if you can help me how to approach this problem. My initial impression was to expand the integrand out...
  43. S

    Area Calculation for Circle and Cardioid Using Double Integrals

    Homework Statement r=1 and r=1+cos(theta), use a double integral to find the area inside the circle r=1 and outside the cardioid r=1+cos(theta) Homework EquationsThe Attempt at a Solution I am confused on the wording and how to set it up. I tried setting it up by setting theta 0 to pi. and r...
  44. yecko

    Line integral of a vector field

    Homework Statement [/B] I would like to ask for Q5b function G & H Homework Equations answer: G: -2pi H: 0 by drawing the vector field The Attempt at a Solution the solution is like: by drawing the vector field, vector field of function G is always tangential to the circle in clockwise...
  45. Q

    Stuck on this integral (using partial fraction decomposition)

    Homework Statement \int\frac{x^2}{\sqrt{x^2+4}}dx Homework Equations n/a The Attempt at a Solution Letting x=2tan\theta and dx=2sec^2\theta d\theta \int\frac{x^2}{\sqrt{x^2+4}}dx=\int\frac{4tan^2\theta}{\sqrt{4+4tan^2\theta}}2sec^2\theta d\theta=\int\frac{8tan^2\theta...
  46. O

    Undergrad Gaussian Quadrature on a Repeated Integral

    Hi there, I am having some difficulty evaluating a repeated integral, which is the first of two shown in the image. I had hoped to be able to use Gaussian Quadrature to provide a numerical result, however am unsure on if this is possible for a repeated integral? I have attempted to use Cauchy'...
  47. B

    Change of variable in an integral

    Homework Statement A massless string of length 2l connects two hockey pucks that lie on frictionless ice. Aconstant horizontal force F is applied to the midpoint of the string, perpendicular to it (see right figure). How much kinetic energy is lost when the pucks collide, assuming they stick...
  48. M

    MHB Checking the Orientation of an Integral on a Surface Bounded by a Sphere

    Hey! :o I want to calculate $$\iint_{\Sigma}\left (ydy\land dz+zdz\land dx+zdx\land dy\right )$$ where $\Sigma$ is the surface that is described by $x^2+y^2+z^2=1$ and $y\geq 0$ and has such an orientation that the perpendicular vectors that implies have a direction away from the point...
  49. D

    MHB Double integral Problem (with solution)

    Evaluate (use attached figure for depiction) $ \iint_{R} \, xy \, dA $ where $R$ is the region bounded by the line $y = x - 1$ and the parabola $y^2 = 2 x + 6$. I will post solution in just a moment with a reply.
  50. Another

    Solving Problem Integral Figure: -256/5 or -96/5?

    Figure for example 1. ∫∫dydx 2. ∫∫x dydx (x2<= y <= 4) and (-2 <= x <= 2) 1. Two method get the same answer 2. Two method get the different answer - between answers 0 or 8 , the correct answer is ? I met this problem with my problem ∫ (x^4 + y^2)dx +(2x^2-y^4)dy = ∫∫ [(4x - ( 2y )]...