10.31.2 Greatest hits from previous weeks

10.31.2.1 Get a "step-by-step" evaluation in Mathematica
10.31.2.2 How do I plot a plane EM wave?
10.31.2.3 Using Export[] sends the file where?
10.31.2.4 How do I get the inverse of a homogeneous transformation matrix?
10.31.2.5 xkcd-style Plots
10.31.2.6 How do I draw a pair of buttocks?
10.31.2.7 Why I get the "Set::write: "Tag Times in is Protected." error?
10.31.2.1 Get a "step-by-step" evaluation in Mathematica

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=148

Is it possible in Mathematica to get a step-by-step evaluation of some functions; that's to say, outputting not only the result but all the stages that have led to it? If so, how does one do it? 
 
... 
[evaluation] [interactive] [faq]
 
asked by Cydonia7 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=44 Score of 146
answered by J. M.'s missing motivation https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=50 Score of 120
10.31.2.2 How do I plot a plane EM wave?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=1987

I would like to display an electromagnetic (EM) wave.  I have written code that works, but it does not "shade" the area between the graph and the axes.  Both the ... 
[graphics] [physics] [visualization]
 
asked by Rainforest Frog https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=202 Score of 24
answered by J. M.'s missing motivation https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=50 Score of 18
10.31.2.3 Using Export[] sends the file where?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=8586

I am trying to use the  Export  command to convert a list of plots into a *.gif file, and the command runs and executes well, but I can't find the file! Where is it ... 
[export]
 
asked by Patrick Da Silva https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1785 Score of 49
answered by Vitaliy Kaurov https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=13 Score of 61
10.31.2.4 How do I get the inverse of a homogeneous transformation matrix?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=106257

I want to get the inverse of this homogeneous transformation matrix: 
 
 iab = { 
{1, 0, 0, 0}, 
{0, 0, -1, 0}, 
{0, 1, 0, 3}, 
{0, 0, 0, 1} 
} 
 
 
using the ... 
[matrix] [linear-algebra] [inverse] [geometric-transform] [rotation]
 
asked by andrestoga https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=37677 Score of 7
answered by march https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=29734 Score of 15
10.31.2.5 xkcd-style Plots

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=11350

I received an email to which I wanted to respond with a xkcd-style graph, but I couldn't manage it. Everything I drew looked perfect, and I don't have enough command over ... 
[plotting] [generative-art]
 
asked by Amatya https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=2039 Score of 644
answered by Simon Woods https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=862 Score of 508
10.31.2.6 How do I draw a pair of buttocks?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=66538

I'm trying to develop a function which 3D plot would have a buttocks like shape. 
 
Several days of searching the web and a dozen my of own attempts to solve the issue have brought nothing but two ... 
[plotting] [graphics3d] [generative-art]
 
asked by Simpleton Jack https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=22399 Score of 356
answered by mikuszefski https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=7608 Score of 557
10.31.2.7 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 11
answered by Mark McClure https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=36 Score of 15