8.41.3 Can you answer these questions?

8.41.3.1 Make curve disappear gradually after Mouse Up

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=277348

I am trying to emulate a feature on GoodNotes that allows me to draw a glowing curve on a graphic and the moment I let go of the mouse, the curve gradually disappears.  See gif below.  The gif is a ... 
[eventhandler]
 

asked by B flat https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=33996 Score of 1

answered by Daniel Huber https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=46318 Score of 0

8.41.3.2 No answer for LyapunovSolve

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=277123

I gave wolfram notebook the code below: 
... 
[wolfram-cloud] [wolfram-alpha-notebook-edition]
                                                                                  

                                                                                  
 

asked by HohO https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=72575 Score of 1

8.41.3.3 General::eivn "Incorrect number 3 of eigenvectors for eigenvalue" when calculating Eigenvectors[FourierMatrix[8]]

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=277306

I just evaluated  Eigenvectors[FourierMatrix[8]]  in Mathematica (version 12.0.0.0) and got a series of errors like: 
 
Eigensystem::eivn: Incorrect number 3 of ... 
[matrix] [bugs] [warning-messages]
 

asked by jcarpenter2 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=60355 Score of 2