8.18.1 Top new questions this week

8.18.1.1 Droplet of water-alcohol mixture spreading due to evaporation-caused surface tension gradient
8.18.1.2 Why FullSimplify return    on this solution of ode?
8.18.1.3 User plug-in methods for SumConvergence
8.18.1.4 simplifying DSolve output. Exponentials raised to constant
8.18.1.5 Why does FindSequenceFunction not work in this case?
8.18.1.6 How to use Unevaluated in postfix version?
8.18.1.7 Two variable recursive integral equation
8.18.1.1 Droplet of water-alcohol mixture spreading due to evaporation-caused surface tension gradient

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=268795

I am trying to solve a coupled system of PDEs for 2 functions  h[t,r]  and  c[t,r] , with initial conditions of ... 
[differential-equations] [equation-solving] [finite-element-method] [physics]
 
asked by James He https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=86544 Score of 8
answered by xzczd https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1871 Score of 11
8.18.1.2 Why FullSimplify return    on this solution of ode?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=268767

I was calling  FullSimplify  with timeout on solution of ode. The idea if it timesout, then will try  Simplify  on same solution ... 
[simplifying-expressions]
 
asked by Nasser https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=70 Score of 8
8.18.1.3 User plug-in methods for SumConvergence

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=268826

@  remarks: 
 
BTW, it is also quite bad that Mathematica does not have Bertrand test. 
 
Is there a way to extend the convergence tests in ... 
[calculus-and-analysis] [summation] [undocumented]
 
asked by Michael E2 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4999 Score of 6
answered by Michael E2 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4999 Score of 7
8.18.1.4 simplifying DSolve output. Exponentials raised to constant

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=268860

I see lots of cases where  DSolve  gives solution that has $e^{c_1}$ in the solution, where $c_1$ is the integration constant. 
When solving this by hand, we normally ... 
[differential-equations] [simplifying-expressions]
 
asked by Nasser https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=70 Score of 5
answered by Michael E2 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4999 Score of 5
8.18.1.5 Why does FindSequenceFunction not work in this case?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=268822

Why does this not work? 
 FindSequenceFunction[{1/2, (2/3)^2, (3/4)^4, (4/5)^6, (5/6)^8}, n] 
(*FindSequenceFunction[{1/2,4/9,81/256,4096/15625,390625/1679616},n]*) 
 
I ... 
[functions]
 
asked by emnha https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=18805 Score of 5
answered by JimB https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=19758 Score of 8
8.18.1.6 How to use Unevaluated in postfix version?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=268861

In the following versions, 
 Thread[Unevaluated@((1 + 2 + 3) (4 + 5 + 6)), Plus] 
Unevaluated[(1 + 2 + 3) (4 + 5 + 6)]~Thread~Plus 
 
I get an expected result 32. 
... 
[mapthread] [unevaluate]
 
asked by Intellectual Gymnastics Loverhttps://mathematica.stackexchange.com/landing/r/digest?cta=user&id=42141 Score of 5
answered by lericr https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=84894 Score of 8
8.18.1.7 Two variable recursive integral equation

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=268967

I'm trying to improve the question posted in Solving an integral vectorial equation by iterations but when the iterations are for two variables. I mean, suposse that I have the following integral ... 
[integral-equations] [nest]
 
asked by Jorge Castaño https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=73029 Score of 4
answered by thorimur https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=63584 Score of 2