neal's profile - activity

I want to operate on mat.

Here is the problem: I have a mat whose value is y/x, and I want to compute the angle of each point in the mat, so I am going to use look-up table for this. But, as you know, the value of tan() between 1-90 degree are always double. So I don't know how exactly to figure this value? Is there anyone can provide me with some advice? Thank you very much!