10.19.1 Top new questions this week

10.19.1.1 Reproducing Ómar Rayo's "Fresh Fog" Painting
10.19.1.2 How to help DSolve obtain this solution to $y'(x)=\sec (y(x))$
10.19.1.3 How to animate an impossible image
10.19.1.4 Why is this RegionFunction not working in my StreamPlot?
10.19.1.5 PolynomialQ behaviour
10.19.1.6 Why do I get different results for the products of two identical expressions?
10.19.1.7 c++ or Mathematica for large eigenvalue problem
10.19.1.1 Reproducing Ómar Rayo's "Fresh Fog" Painting

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=304043

Ómar Rayo 
Ómar Rayo (1928 - 2010) was a Colombian painter best known for his 
op-art paintings. He completed his first drawing studies at an 
academy in Buenos Aires. In 1960 he received a Guggenheim ... 
[graphics] [computational-geometry] [generative-art]
 
asked by eldo https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=14254 Score of 19
answered by azerbajdzan https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=53172 Score of 20
10.19.1.2 How to help DSolve obtain this solution to $y'(x)=\sec (y(x))$

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=303980

V 14 
 ode = Cos[y[x]]*y'[x] == 1 
ic = y[0] == 2 
DSolve[{ode, ic}, y[x], x] 
 
 
Anything can be done to help DSolve obtain the following solution? 
Hand solution 
\begin{... 
[differential-equations] [calculus-and-analysis]
 
asked by Nasser https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=70 Score of 9
answered by Michael E2 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4999 Score of 8
10.19.1.3 How to animate an impossible image

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=304014

Could someone help me generate movement for this image 
This image is like an impossible figure, yet I have seen similar ones but I can't imagine how to give it movement. 
thanks in advance 
[graphics] [image-processing] [animation] [rotation]
 
asked by zeros https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=26849 Score of 7
answered by cvgmt https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=72111 Score of 16
10.19.1.4 Why is this RegionFunction not working in my StreamPlot?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=304120

I am trying to bound the plotting region inside a  StreamPlot  using  RegionFunction with a piecewise equation. Here's the code: 
<... 
[plotting] [streamplot]
 
asked by zurg https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=73123 Score of 6
answered by Goofy https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=46569 Score of 5
10.19.1.5 PolynomialQ behaviour

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=304055

I am crafting some functions on polynomials that must be in x. But I checked that it is always True whatever variable I use: 
... 
[symbolic] [polynomials] [algebra]
 
asked by Giovanni Russo https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=90454 Score of 6
answered by Greg Hurst https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4346 Score of 7
10.19.1.6 Why do I get different results for the products of two identical expressions?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=304035

I have two expressions with the Gamma function that are identical: 
... 
[numerics] [special-functions] [products]
 
asked by Vaclav Kotesovec https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=29655 Score of 6
answered by Daniel Lichtblau https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=51 Score of 5
10.19.1.7 c++ or Mathematica for large eigenvalue problem

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=303954

I need to find eigenvalues of very large matrices ($10^7\times 10^7$). To be precise: I only need the lowest eigenvalues (lets say the 100 lowest). Most of the matrix elements are zero ($\approx 99,... 
[eigenvalues] [c++]
 
asked by ZaraReinm. https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=98417 Score of 4
answered by Henrik Schumacher https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=38178 Score of 6