# All Questions

59,222 questions
39 views

### Issues solving system of differential equations [on hold]

d = NDSolve [{x''[t] == (x [t] + a[t])/(-2), a''[t] == -x''[t]/2, x[0] == 0, x'[0] == 1, a[0] == 0, a'[0] == 0}, {x, y}, {t, 20}] Keeps returning the error "To ...
38 views

### How do I divide an integral into parts and sum the total?

I have an exercise looking like this: Analyze the integral $4\int_{0}^{1} \sqrt{1-x^2}\ \tex$ numerically by ng the interval (2,1) into three equal parts, then summarize the integral parts. I just ...
13 views

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### VoronoiMesh with custom distance function

I'm failing at reading the documentation. Is there a way to specify the distance function used by VoronoiMesh? As a stripped down example say I have a rank-1 lattice such as: ...
36 views

### DistributionFitTest` for 2D data [on hold]

How can I make DistributionFitTest accept 2D data? According to the Documentation - it should be able to accept multivariate data, and the test distribution can be ...
24 views

### Selecting specific elements of a list

Suppose we have the following list: ...
30 views

### How to force Mathematica not to show the result in numerical format [on hold]

I have a function f[x_] = 4/3 x. However, Mathematica displays it as 1.3333 x. How to force it to display the function in the form 4/3 x?
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### How do I plot a function that contains variables I have previously defined?

I am trying to plot t as a function of the variable EE which is itself included in variables I have defined. However, when I ...
23 views

### Discretize Graphics3D with Scale and Rotate?

How can I discretize a Graphics3D object that makes use of Scale and Rotate? When I try <...
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### How to plot this set $M\subset\mathbb{R}^3$?

Is there a way to plot the following set with Mathematica? $M=\left\{ \left(x,y,z\right)\mid x\in\mathbb{R}\:,\:y=\left|x\right|\:,\:0\leq y<z\right\}$ I think it's suppose to look something like ...
96 views

### Strange behavior of Out[]

Let's create two notebooks external.nb and primary.nb. Then call the external.nb notebook from the primary.nb and investigate values of Out[ ]. The context of the external notebook is not important, ...
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### Liquefying of Nitrogen & Oxygen Gaseous to Liquid Phase. Thermodynamics. How to plot solution? Solved

Process of Liquefying of air composed of 79% Nitrogen & 21% Oxygen from Gaseous to Liquid Phases as Follows: 1) When Temperature is higher than T>83 k they both are gas. 2) at T=83 k and less ...
29 views

### How to create dynamic PlotLegends?

How to add dynamic PlotLegends to the below code? ...
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### Using Dynamic[] function

I would like to use Dynamic[] to print progress of evaluation of some function, which works quite long. let's say that the definition of ...
40 views

### Mathematica problems [on hold]

What means when this message in mathematica program Factor[Solve[E3 == 0, b2]]={}, such that in the expression of E3 there is b2.
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### How to compute delta coefficients in mathematica

I want to get delta coefficients calculated. The definition can be found here. However, I don't know what to do with the minus indices. I have tried computing it in a slightly different way, namely: <...
35 views

### How to automatically transform Abs[Cos[x]]Sec[x] to Sign[Cos[x]]?

Out of some simplification, the term Abs[Cos[x]]Sec[x] appears. How can I make the code automatically transform ...
48 views

### Workbench documentation build fails

My old installation of Workbench went inexplicably wrong, so I tried a fresh install of Eclipse & Workbench. Looks good until I try Documentation Build, when I get the following error: An ...
23 views

### Convincing Reduce[] to work

The following should return True: Reduce[ForAll[{t, x}, x > 0, Exists[y, x^t == y]],Reals] but ...
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### Finding the amplitude of function solved using ParametricNDSolve

I have been trying to find the peaks of a function I have plotted using ParametricNDSolve. I have to find these peaks to calculate the amplitude of all the various waves in the observed output. By ...
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### numpy.linalg.solve returns a solution for a matrix that is not full rank [migrated]

I've been learning the basics of OLS regression, and was told that there can't be perfect multicolinearity in the model. I have a matrix that is obviously not of full rank: ...
21 views

### Limiting value problem with Plot3D [on hold]

When running this code ...
18 views

### Moving to the last placeholder with inputautoreplacements

I have had a long-standing problem when I try to use my inputautoreplacements in a text cell. The replacements I have made include boxes that include placeholders. When in the text cell, you type ...
74 views

### Second Derivative in MMA

I would like to ask, why the following second derivative is wrong in MMA ...
40 views

### how to linearize an equation? [migrated]

How does one linearize this equation?
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### DisplayForm problem with pi in FractionBox

The following line produces an output with the text "Pi" displayed instead of the symbol for pi. All help with an alternative or correction of this would be much appreciated, thank you.
173 views

### The multiplication of list of matrices

I need to multiply 3 lists of matrices (b.a.b) as the following code ...
75 views

### Conditional evaluation: black hole cross section

I'm trying to calculate the collision cross section of black holes, more precisely, I want the critical impact parameter $b_{\text{crit}}$ for a given initial velocity $v$ such that, at this speed, ...
124 views

### Imaginary part of expression too difficult to calculate

I am trying to calculate the imaginary part of a long expression. It's a long enough expression that Mathematica "hangs" when you run: ...
29 views

### Why OpenerView reduces the size of my equation

In this code the equation comes out with the right size. ...
28 views

### Having difficulties using results returned by Solve

I'm new to Mathematica, and I am still having some issues figuring out the general syntax. I've got to use Mathematica, as my research requires a powerful symbolic math program. I'm having trouble ...