Questions tagged [calculus-and-analysis]

Questions related to the calculus and analysis branches of Mathematica, including, but not limited to, limits, derivatives, integrals, series, and residues.

363 questions with no upvoted or accepted answers
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16
votes
0answers
334 views

Strange behaviour of integrals with Cos, Sin, and Exp

Bug introduced in 8.0.4 or earlier and persisting through 11.0.1 During the study of the problem How to solve this integration? I have discovered a strange behaviour of some integrals. I would ...
12
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0answers
302 views

Is there a way to teach integrate new solutions?

I have an integral which I can solve, but integrate cannot: ...
10
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0answers
155 views

Workaround for DSolve in V 12 when it gives undefined as solution to 1D heat PDE?

Reported to WRI CASE: 4278450 Comparing the following, all done from clean kernel The strange thing is that V 12 can solve this same PDE without the assumptions ...
10
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0answers
267 views

Possible Symbolic Integration Bug

Bug introduced between 5 and 8 and persisting through 12.0. I think I may have found a bug, and want to verify is this reproducible in other versions and platforms and not a mistake of mine. I ...
9
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0answers
109 views

Finding simplifying substitutions for an integral involving limits and integrand

[The following is based on a William Lowell Putnam Mathematical Competition problem.] Consider the definite integral: $I = \int\limits_2^4 \frac{\sqrt{\log (9-x)}}{\sqrt{\log (9-x)}+\sqrt{\log (x+3)}...
8
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0answers
101 views

Bug in integral related to beta distribution

I've encountered a problem, which I'm pretty sure is a bug. I've contacted Wolfram's support and they were less than helpful. I'd like to bring the issue up here to get either a confirmation that it ...
8
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0answers
355 views

Expansion for Modified Bessel Function Around Infinity

I'm somewhat new to Mathematica, and I don't understand why I'm getting inconsistent series expansions for the modified Bessel Function of first kind near $x=\infty$. First problem: I get different ...
8
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0answers
188 views

MacDonald formula for Modified Bessel Functions

How can I make Mathematica understand these two integrals? $$\int_0^{\infty} e^{-x \cosh{\xi}} d\xi = K_0(x)$$ $$\int_0^{\infty} e^{-\frac{1}{2} \Big( \frac{x y}{u} + u \frac{x^2+y^2}{x y} \Big) } K_{...
8
votes
0answers
242 views

Incorrect evaluation for Thue-Morse signed harmonic series

I would like to evaluate $$s = 1 - \frac{1}{2} - \frac{1}{3} + \frac{1}{4} - \frac{1}{5} + \frac{1}{6}+\frac{1}{7}-\frac{1}{8} - ... + \frac{(-1)^{\textrm{binary digit sum}(n-1)}}{n} + ... $$ where ...
7
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0answers
124 views

A bug in Derivative?

Update This is a bug in v11.3 or earlier and is fixed in v12. Original Post Check this out: ...
6
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0answers
166 views

Mathematica gives wrong answer for a definite integral

I tried to compute the definite integral Integrate[Exp[Pi I t]/((-I + 1 + t) Cosh[Pi t]), {t, -Infinity, Infinity}] and obtained the answer (version 11.2.0.0) ...
6
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0answers
66 views

Why does Mathematica recognize the conditional convergence of some integrals but not others?

Consider the following two polynomials: f1[t_] := t^3 - 1 f2[t_] := t^3 + 3t - 1 Both of these polynomials have a single real root: $f_1(t)$ at $t = 1$, and $...
6
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0answers
353 views

Integrating rational functions of several variables over $\mathbb{H}^4$

Let $W$ be a rational function of $8$ variables $a,b,c,d,e,f,g,h$ from this file, e.g.: ...
6
votes
0answers
141 views

Convoluting inverse square root with Gaussian

Bug introduced in 9.0 and persisting through 11.0.1 or later I would like to convolute the inverse square root on the interval [0,inf] with a Gaussian function, ...
6
votes
0answers
239 views

Strange Integrate behavior (a bug!)

The following two calculations should give the same result. After all, integration is a linear operation. I have pasted the code below in case you want to play with it. ...
5
votes
0answers
118 views

Integrate under assumptions

I am trying to solve the following integral: $$\int_0^\infty u^{\sigma-1} \exp\left[-c u^\sigma\right] \mathrm{d}u$$ under the assumptions $\sigma \in (0,1)$ and $c>0$. I know the result is $$\...
5
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0answers
420 views

Convergence of approximate solutions to obstacle problem for the heat equation

Consider the problem $$(P) \qquad \begin{cases} \min\{\partial_t u - \Delta u, u -\varphi \} = 0 & \text{ in } (0,T)\times \mathbb{R}^N \\ u(0,\cdot) = \varphi(0,\cdot) & \text{ in } \mathbb{...
5
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0answers
185 views

Integrate producing bad result

Bug introduced in 9.0 or earlier, and fixed in 10.2 I noticed a bug in Mathematica. It computes incorrectly a definite integral ...
5
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0answers
155 views

Using NIntegrate and DiscretePlot to visualize pseudodifferential operators

In harmonic analysis, pseudodifferential operators are a way to generalize the notions of derivatives, through the use of Fourier transforms. The basic idea being, Let $u(x)\in\mathcal{S}(\mathbb{R}^...
5
votes
0answers
142 views

Derivative of generating function (Example from documentation)

Bug introduced in 9.0 or earlier and persisting through 11.0.1 or later In the documentation for GeneratingFunction, the following example is given under Examples -...
5
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0answers
190 views

Calculating a limit with a result that is discontinuous in the parameters

The following limit is left unevaluated (Edit: added the assumption that $\epsilon$ is real thanks to the comment below): ...
4
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0answers
54 views

Computing differentials on a manifold

Consider $\phi:SO(3) \to \mathbb{R}^3$, $R \mapsto (R^\top e_3)\times e_3$ where $R$ is a real $3\times 3$ orthogonal matrix and $e_3 = [0\ 0\ 1]^\top$. Can Mathematica compute the differential of $\...
4
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0answers
60 views

How to calculate specific area on surface of sphere?

I am trying to calculate the solid angle subtended by arbitrary-shaped loops on a sphere's surface. First, I parametrize circular loops by: $$\theta(t,k_{x0},r) = k_{x_0} + r \cos(t);$$ $$\phi(t,k_{...
4
votes
0answers
98 views

Trigonometric integral with assumptions fails

Consider the following integral Assuming[Element[{n, m}, Integers] && n >= 0, Integrate[Cos[ϕ]^n Exp[I ϕ m], {ϕ, 0, 2 π}]] ...
4
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0answers
97 views

Integrating a product of three Spherical Harmonics

The following command is returned unevaluated. The answer is well known to be related to Wigner's 3j Symbol which is also a defined function in Mathematica. ...
4
votes
3answers
277 views

Evaluate a certain two-dimensional integral involving an inverse hyperbolic tangent

Evaluate the integral of ...
4
votes
1answer
271 views

Implementing positivity constraints over a six-dimensional hypercube

This question involves the same subject matter as my previous one (How can one achieve the most accurate estimates of certain six-dimensional integrals under specific constraints?), but with another (...
4
votes
0answers
124 views

Integral Representation of DiracDelta

I would like to get dirac delta from integral definition, of course if I ask Integrate[Exp[I x t],{x,-Infinity,Infinity}] I get that the integral does not ...
4
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0answers
111 views

Total variation integration of a discontinuous function

This question derives from this one, about mathematics and Maple. Consider the following discontinuous function: ...
4
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0answers
271 views

What kind of algorithm does Mathematica use to find limits?

Is there any information available about the implementation of the Limit command? In particular, I am interested in how Mathematica computes limits of real ...
4
votes
0answers
104 views

Possible bug in Integrate

The integral I'm considering is: $\int_0^{2\pi}\frac{e^{\pm t\theta}}{4\sinh^2\left(\frac{s+ i\theta}{2}\right)} = 2\pi e^{\mp s}\Theta(\pm s)$ for $s\neq 0$ (otherwise there some other subtleties). ...
4
votes
0answers
128 views

How to verify the convexity of a function?

I have an optimization problem with the following objective function in $(x,y)$ $$ A\log \left(\sum_{i=1}^n x_i\right)+\log\left(1-\frac{f}{n}\left(\sum_{i=1}^n\frac{x_i}{y_i}\right)\right) $$ where $...
4
votes
0answers
86 views

Huge difference after changing a fraction to decimal

I have a limit to calculate. With[{p = 1/2, q = 0.1}, Limit[a^q Integrate[Sin[x]/x^p, {x, a, Infinity}], a -> Infinity]] gives correct result ...
4
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0answers
150 views

Exploring formal limit definition

I found a few demonstrations on the Wolfram Demonstration Project site that help users to explore the formal definition of a limit. That is, $$\lim_{x\to a}f(x)=L$$ if and only if for every $\epsilon&...
4
votes
1answer
225 views

Integral of DiracDelta giving an unusual answer

I have been getting a number of seemingly inconsistent solutions to integrals of Dirac delta functions in which the integrand evaluates to DiracDelta[0] at one of ...
4
votes
0answers
306 views

Strange behaviour of MMA in derivatives of some standard functions

There are some peculiar things to be discovered in derivatives of some standard functions in MMA: Strange behaviour Example 1: Abs We have ...
4
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0answers
1k views

Symbolic matrix calculus: What's new in Version 9

I have seen some of the related posts, which ask about doing matrix calculation on tensors unknown dimensions. One of the posts mentioned that version 9 has some capability, but it was concerned about ...
4
votes
0answers
211 views

Linearised Einstein equations

I need to compute the linearised Einstein Equations around a fixed metric $$g_{μν}=\text{Minkowski metric} + h_{μν}$$ which is not the flat metric. Does anyone know a Mathematica package or a ...
4
votes
0answers
548 views

Spherical harmonic derivative

Consider the following substitution Derivative[2, 0][S][th, ph] /. S -> Function[{th, ph}, SphericalHarmonicY[3, 0, th, ph]] which gives correct answer. While ...
3
votes
0answers
104 views

How to test whether an improper integral converges or diverges?

To verify the improper integral $\int_{1}^{\infty}x\cdot\left | \sin (x^4)\cdot\sin x \right |dx$ converges or diverges,I code ...
3
votes
0answers
110 views

Evaluate $\int_0^1 \frac{\log \left( 1+x^{2+\sqrt{3}}\right)}{1+x}\mathrm dx$

Saw this post and noted that it was posted back in 2013. Just tried V11.3 and got no analytic solution. Just wondering if there is a way for Mathematica to give the desired result? Machine VS Human ...
3
votes
0answers
85 views

Analytic Integration Bug of Hypergeometric function in Version 11.3?

I got this integral ...
3
votes
0answers
81 views

Is Mathematica doing this integral of a wave form approximation correctly?

I am trying to integrate a square wave approximation I found in this answer by ybeltukov. Nothing wrong with the answer but when I try to integrate it I run into trouble. I modified the code from ...
3
votes
0answers
142 views

How can I solve a nonlinear fractional order integro-differential equation?

How do I solve the nonlinear fractional order integro-differential equation shown above in Mathematica?
3
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0answers
55 views

Definite integals that can be expressed in terms of itself

I came across the integral $\int_0^\infty \frac{1}{\left(x^2+1\right) \left(x^{2015}+1\right)}\,dx$ in a Youtube video. It apparently appeared in the MIT Integration Bee of 2015. In the video, it was ...
3
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0answers
74 views

Extract explicit region (integration bounds) from ImplicitRegion

Using an ImplicitRegion in NIntegrate by far best performance is obtained by using ...
3
votes
0answers
240 views

Integrating the Associated Legendre Polynomials

I know the following identity: $\qquad \int_{-1}^1 P_l^m(t)^2dt=\frac{2(m+n)!}{(2n+1)(n-m)!}$ I would like to verify this result using Mathematica. This is what I entered: ...
3
votes
0answers
37 views

Truncated in time derivation

I have follogwing equations: $E(n) = \frac{1}{2} ||\vec{\epsilon}(n)||^2$ with $\vec{\epsilon}(n) = \vec{y}_{target}(n) - \vec{y}_{prediction}(n) $ where n denotes a discrete time. $\vec{y}_{...
3
votes
0answers
82 views

Why Integrate does not work in the first call?

Consider an example (calculated in Mathematica 11.0.1.0): ...
3
votes
0answers
141 views

Negative result of a integral of positive function

Let's try this: I have a function of two arguments, $e$ and $\omega$. First I integrate some function of $(e, \omega)$: ...