8.31.2 Greatest hits from previous weeks

8.31.2.1 Smiley Face using parametric equations
8.31.2.2 How to add a front-end to the free Wolfram Engine?
8.31.2.3 Why I get the "Set::write: "Tag Times in is Protected." error?
8.31.2.4 Make a scatter plot from two lists
8.31.2.5 Fastest way to generate   a,a , a,b , a,c , b,b , b,c , c,c   from  a,b,c
8.31.2.6 Why round to even integers?
8.31.2.7 How to plot an ellipse?
8.31.2.1 Smiley Face using parametric equations

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=137669

I need to know the parametric equations for this smiley face and how to draw it in Mathematica.  I'm completely lost. 
[plotting] [parametric-functions] [homework]
 
asked by Woeseph https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=46575 Score of 1
answered by Bob Hanlon https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=9362 Score of 5
8.31.2.2 How to add a front-end to the free Wolfram Engine?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=198839

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] [free-wolfram-engine] [jupyter-notebook]
 
asked by Alexey Golyshev https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=23402 Score of 77
answered by Alexey Golyshev https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=23402 Score of 64
8.31.2.3 Why I get the "Set::write: "Tag Times in is Protected." error?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=11868

Why I get the error below with this code: 
 
... 
[vector-calculus]
 
asked by Aurelius https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1669 Score of 10
answered by Mark McClure https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=36 Score of 13
8.31.2.4 Make a scatter plot from two lists

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=21884

I have two lists of values 
 
 xx = {0.1, 0.3, 0.35, 0.57, 0.88, 1.0} 
yy = {1.2, 3.5, 4.5, 7.8, 9.0, 12.2} 
 
 
I want to make a scatter plot (list plot) with xx as x ... 
[plotting]
 
asked by JACKY88 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=2403 Score of 28
answered by Eric Thewalt https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=6313 Score of 42
8.31.2.5 Fastest way to generate   a,a , a,b , a,c , b,b , b,c , c,c   from  a,b,c

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=268651

What is the fastest way to generate  {{a,a},{a,b},{a,c},{b,b},{b,c},{c,c}}  from  l={a,b,c} ? I've tried 
... 
[list-manipulation] [permutation]
 
asked by Thrash https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=86530 Score of 15
answered by yode https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=21532 Score of 15
8.31.2.6 Why round to even integers?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=2116

According to the Mathematica help: 
Round rounds numbers of the form x.5 toward the nearest even integer. 
For example: 
 
 Round[{0.5, 1.5, 2.5, 3.5, 4.5}] 
 
 
gives 
... 
[numerics] [language-design]
 
asked by wxffles https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=427 Score of 84
answered by Per Alexandersson https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=488 Score of 52
8.31.2.7 How to plot an ellipse?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=20100

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 ... 
[plotting]
 
asked by Sriram https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=6075 Score of 19
answered by Jens https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=245 Score of 32