8.40.3 Can you answer these questions?

8.40.3.1 How to test scalar product variables against each other?

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=277028

Curious if there is a way to save time with scalar product multiplication with several variables? 
I have a 8x4 matrix and i wanna check if all the columns are orthogonal with each other, so ive taken ... 
[list-manipulation] [matrix] [linear-algebra] [vector]
 

asked by Robin Petersson https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=89362 Score of 1

answered by Daniel Huber https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=46318 Score of 0

8.40.3.2 MemoryConstrained[] does not work as expected

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=276902

I am trying to put an upper limit on how much memory the kernel can use. For this, I am using the MemoryConstrained function in Mathematica. But this behaves very weirdly as shown below. 
... 
[memory]
 

asked by jar- https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=80750 Score of 2

8.40.3.3 3D plot is noisy

https://mathematica.stackexchange.com/landing/r/digest?cta=question&id=277064

I have the following 3x3 matrix, dependent on the variables $k_{x}$,$k_{y}$ : 
... 
[plotting] [graphics] [eigenvalues]
 

asked by Mathew https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=85436 Score of 1

answered by cvgmt https://mathematica.stackexchange.com/landing/r/digest?cta=user&id=72111 Score of 0