11.9.1 Top new questions this week

11.9.1.1 How to use RegionDilation correctly
11.9.1.2 NSolve hangs on second invocation
11.9.1.3 How can I use Manipulate to rotate a 3D figure?
11.9.1.4 How can we simplify this algebraic expression involving square roots?
11.9.1.5 How to Reorder Piecewise Function Compositions
11.9.1.6 How to fill and calculate the region a rotating and moving stick swept?
11.9.1.7 How can I draw the centers of the circles and calculate the volume of the solid?
11.9.1.1 How to use RegionDilation correctly

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=311482

I'm trying to use  RegionDilation  on a crescent shape. 
What am I doing wrong? 
... 
[bugs] [geometry] [computational-geometry]
 
asked by rak1507 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=107083 Score of 7
answered by cvgmt https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=72111 Score of 4
11.9.1.2 NSolve hangs on second invocation

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=311446

I've run into an interesting glitch with  NSolve , and wonder if anyone here might have an insight into what's going on. 
Starting with a fresh kernel, the command 
<... 
[equation-solving] [bugs]
 
asked by Andrew Neitzke https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1095 Score of 7
answered by Michael E2 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4999 Score of 3
11.9.1.3 How can I use Manipulate to rotate a 3D figure?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=311438

I have this code 
 Plot[Piecewise[{{2 Sqrt[1 - x^2/16], -4 <= x <= 0}, {Sqrt[4 - x^2], 0 <= x < 2}}], {x, -4, 2}] 
 
 
I used ... 
[revolutionplot3d]
 
asked by Laurenso https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=87428 Score of 7
answered by cvgmt https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=72111 Score of 11
11.9.1.4 How can we simplify this algebraic expression involving square roots?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=311485

While performing some analytical calculations, I got the following large expression when I was expecting just  Sqrt[a^2 + b^2] . To my surprise, Mathematica seems to ... 
[simplifying-expressions] [symbolic] [algebraic-manipulation] [assumptions]
 
asked by WillG https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=59634 Score of 6
answered by Michael E2 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4999 Score of 5
11.9.1.5 How to Reorder Piecewise Function Compositions

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=311539

I'm conducting compositions of piecewise functions and Mathematica is producing correct output but I want to reorder the output on the interval [0,1]. For example the code below 
... 
[simplifying-expressions] [function-construction] [formatting] [functional-style]
 
asked by user42700 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=42700 Score of 5
answered by march https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=29734 Score of 5
11.9.1.6 How to fill and calculate the region a rotating and moving stick swept?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=311520

Assume a stick  Line[{{0, 0}, {0, 1}}] , one end is A(0,0) and the other end is B(0,1). The stick is rotating around A counterclockwise with angular frequency 2*Pi ... 
[calculus-and-analysis] [regions] [area]
 
asked by metroidman https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=94488 Score of 5
answered by azerbajdzan https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=53172 Score of 4
11.9.1.7 How can I draw the centers of the circles and calculate the volume of the solid?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=311450

Based on the  manual I tried to draw this figure 
 
My code 
... 
[graphics3d] [parametricplot3d]
 
asked by minhthien_2016 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=5320 Score of 5
answered by Roderic https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=76085 Score of 9