6.12.2 Greatest hits from previous weeks

6.12.2.1 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: 
 
Needs["VectorAnalysis`"] 
 
 = 1000; 
g = 9.80665; 
 = 0.001; 
p[x_, y_, z_, t_] = {x^2, Sqrt[y], -z, t^3}; 
f[x_, y_, z_, t_] = {-x^2, Sqrt[y]/2, z, t^2}; 
 
  ... 
[vector-calculus]
 

asked by Aurelius https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=1669 10 votes

answered by Mark McClure https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=36 13 votes

6.12.2.2 What are the most common pitfalls awaiting new users?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=18393

As you may already know, Mathematica is a wonderful piece of software. 
However, it has a few characteristics that tend to confuse new (and sometimes not-so-new) users. That can be clearly seen from  ... 
[programming] [core-language] [faq] [guidelines]
 

asked by Dr. belisarius https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=193 462 votes

answered by Michael E2 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4999 279 votes

6.12.2.3 Is it possible to export the equations from Mathematica to MATLAB?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=14035

Is it possible to export the output expressions from Mathematica computations (e.g., equations) in valid MATLAB syntax? 
 
[export] [matlab]
 

asked by Seyhmus Güngören https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=4256 41 votes

answered by rm -rf https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=5 48 votes

6.12.2.4 Generate a Unit Circle Trigonometry

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=2456

Struggling often with Trigonometry I would like to have some code to generate this Unit Circle Trigonometry. Would be of great help when I need to transform some data : 
 
 
 
[graphics] [trigonometry]
 

asked by 500 https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=172 18 votes

answered by Mark McClure https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=36 32 votes

6.12.2.5 How to find the position of elements in a list satisfying criteria

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=180

Say I have a list x={2,4,6,8,10} and I want to find out the positions of the elements that are greater than 7. 
 
Select[x, #>7&] gives the elements themselves, and Position[x,8] gives the  ... 
[list-manipulation]
 

asked by PeterR https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=140 64 votes

answered by J. M.'s technical difficultieshttps://mathematica.stackexchange.com/landing/r/digest?cta=user&id=50 62 votes

6.12.2.6 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=44 125 votes

answered by J. M.'s technical difficulties https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=50 105 votes

6.12.2.7 Is there any algorithm that runs faster in Mathematica than in C or Fortran?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=208045

I'm just curious. My friend just told me that Mathematica is mostly for symbolic calculation and not efficient for Numerical computations. He told me that's the reason most of the people don't use  ... 
[performance-tuning] [function-construction]
 

asked by Gummala Navneeth https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=66938 44 votes

answered by Szabolcs https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=12 73 votes