3.18.2 Greatest hits from previous weeks

3.18.2.1 How can Mathematica be used to create images like these?

http://mathematica.stackexchange.com/questions/118992/how-can-mathematica-be-used-to-create-images-like-these

 
Here are two examples of artistic image interpolation using just black lines: 
 
 
TRIANGULATION: ANGULAR CELEBRITIES DRAWN WITH A PEN 
Interpolation for Triangulation-represented Digital Image 
 
 
The  ...
 

- asked by R Hall (28 votes), answered by MarcoB (29 votes)

3.18.2.2 How to tell Mathematica that certain variables are real/imaginary, integer-valued, etc

http://mathematica.stackexchange.com/questions/66273/how-to-tell-mathematica-that-certain-variables-are-real-imaginary-integer-value

 
I'm trying to expedite some quantum mechanical calculations by running them through Mathematica. Expectation values and stuff like that. When I say, for example, 
 
u[x_] := Sqrt[2/L] * Sin[Pi * n * x /  ...
                                                                                  

                                                                                  
 

- asked by Matthew Brunetti (8 votes), answered by SquareOne (6 votes)