 ## Top new questions this week:

### Mathematica v12 Integration bug?

After upgrading to mathematica 12, this integral gives the wrong result, also with other types of similar integrals. Integrate[t*Exp[t],t] The output Exp[t^2]/2 is wrong (it should ...

version-12 asked by mastrok 15 votes

### Why use \[FormalN]?

Through a copy of some code from an answer on this site I discovered the existence of: \[FormalN] The documentation describes it as follows: "Used to represent a formal parameter that will never ...

programming documentation asked by nilo de roock 15 votes answered by Sjoerd Smit 15 votes

### Convert symbolic to numeric code: speed up morphing

Recently I asked a question about the morphing between two functions and got two excellent answers. The accepted answer is using the continuous optimal transport theory. This seems to be very suitable ...

equation-solving numerical-integration asked by yarchik 12 votes answered by Federico 9 votes

### How to fill a closed parametric curve?

I have a curve in parametric form: ParametricPlot[{(1 - Cos[2 \[Pi] s]) Sin[2 \[Pi] s], Cos[2 \[Pi] s] (Sin[2 \[Pi] s] + 1)}, {s, 0, 1}, Axes -> False, PlotStyle -> Black] This gives: ...

plotting filling asked by tst 11 votes answered by kglr 17 votes

### Simplify makes Mathematica forget that a matrix is Hermitian

Using Simplify with certain trivial assumptions makes Mathematica forget that a given matrix is Hermitian. See the minimal example below: expr = Exp[I*2*π*Re[n]] mat = {{Re[n], a*expr}, ...

matrix simplifying-expressions linear-algebra assumptions asked by Hannebambel 8 votes answered by mikado 8 votes

### Can Mathematica achieve this diagram?

Can Mathematica be used to create diagrams of drift diffusion of the kind shown, including histograms showing the response-time distributions? The distributions capture the time taken by a random ...

plotting histograms asked by user120911 8 votes answered by Michael E2 16 votes

### Reverse color of overlapping points?

Is there a simple way to change the color of the region where two Points overlap? For example in Graphics[{PointSize, Point[{1, 1}], Point[{0, 0}]}], the resulting two points have an area where ...

plotting graphics asked by Nicholas G 7 votes answered by Carl Woll 5 votes

## Greatest hits from previous weeks:

### Even Fibonacci numbers

Today, I found the Euler Project. Problem #2 is Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be: 1, ...

number-theory project-euler asked by xyz 34 votes answered by rcollyer 45 votes

### Can Mathematica do symbolic linear algebra?

For instance, is there some way I can say "let A and B be arbitrary real $m\times n$ and $k\times m$ matrices, Simplify[Transpose[Transpose[A].Transpose[B]]]" and Mathematica would simplify it to B.A? ...

linear-algebra symbolic asked by Niki Estner 57 votes answered by Mauricio de Oliveira 15 votes

### How to plot an ellipse?

I'm new to Mathematica, and I'm finding it difficult to plot an ellipse. I tried using Plot[(x/5)^2 + (y/3)^2 == 1, {x, -5, 5}, {y, -3, 3}] but I'm getting some errors. Is there something wrong ...

plotting asked by Sriram 15 votes answered by Jens 26 votes

### Multivariable Taylor expansion does not work as expected

The basic multivariable Taylor expansion formula around a point is as follows:  f(\mathbf r + \mathbf a) = f(\mathbf r) + (\mathbf a \cdot \nabla )f(\mathbf r) + \frac{1}{2!}(\mathbf a \cdot ...

calculus-and-analysis series-expansion asked by matheorem 53 votes answered by Jens 59 votes

### Help find a bright object on Mars!

In today's news, scientists found a bright object on one of Curiosity's photos (it's near the bottom of the picture below). It's a bit tricky to find - I actually spent quite some time staring at the ...

image-processing asked by Victor K. 197 votes answered by Niki Estner 256 votes

### How to add a front-end to the free Wolfram Engine?

https://blog.stephenwolfram.com/2019/05/launching-today-free-wolfram-engine-for-developers/ http://www.wolfram.com/engine/ The Free Wolfram Engine for Developers is available for pre-production ...

front-end jupyter-notebook asked by Alexey Golyshev 51 votes answered by Alexey Golyshev 46 votes

### How to express trigonometric equation in terms of of given trigonometric function?

How can I express a trigonometric equation / identity in terms of a given trigonometric function? using following trigonometric identities Sin[x]^2+Cos[x]^2==1 Sin[x]/Cos[x]==Tan[x] ...

functions trigonometry asked by Prashant Bhate 30 votes answered by Simon 37 votes

## Can you answer these questions?

### Access to quantities other than parameter values in in StepMonitor for NonlinearModelFit?

NonlinearModelFit obviously does a lot of internal calculations at each step, including determining the Response (the value of the fitting function for the current values of the parameters evaluated ...

nonlinear monitoring asked by Kevin Ausman 1 vote

### The replacement function is an integral and the double integral yields a different answer than the normal double integral

I am fairly new to Mathematica. I have a quick inquiry. The code is simple and just 3 lines. Trying to do a replacement rule as follows ruletrr = intsl[exp_] :> Integrate[exp, {u, u, 1}] ...

replacement asked by Ehab Wilson 1 vote

### Why does FindInstance take so long: It is faster with more restrictions than with less?

A support case with the identification [CASE:4347836] was created. I just noted this little puzzle on twitter by Brillant.org: \begin{align} A B C\\+ BCA\\ = CDE \end{align} Given that $A$ is ...

equation-solving error findinstance asked by gwr 3 votes
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