4.13.2 Greatest hits from previous weeks

4.13.2.1 How to make a Spherical Cow?

http://mathematica.stackexchange.com/questions/125043/how-to-make-a-spherical-cow

 
Being a theoretical physicist, I always have a great respect for Spherical Cow. So I thought about making one myself. I am not sure how can I create (something considered to be the simplest!) this  ...
 

- asked by Sumit (60 votes), answered by andre (69 votes)

4.13.2.2 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 (expectation values etc.) by running them through Mathematica. When I say, for example, 
 
u[x_] := Sqrt[2/L] * Sin[Pi * n * x / L] 
 
 
and then  ...
 

- asked by Matthew Brunetti (13 votes), answered by SquareOne (10 votes)