## 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[2]*Exp[t[2]],t[2]] The output Exp[t[2]^2]/2 is wrong (it should ...

version-12

### 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

### 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

### 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

### 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

### 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

### 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[2], Point[{1, 1}], Point[{0, 0}]}], the resulting two points have an area where ...

plotting graphics

## 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

### 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

### 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

### 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

### 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

### 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

### 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

## 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