Tests for range of the spherical angle

[mmikhasenko]

Closes #20

Checklist

• Tests are passing
• Docs were updated and workflow is passing
• add Test

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.91%. Comparing base (46d7df1) to head (cc082b2).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #22   +/-   ##
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  Coverage   93.91%   93.91%           
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  Files           4        4           
  Lines         148      148           
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  Hits          139      139           
  Misses          9        9           

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[szabo137]

I think the current implementation does what you need because the two-argument atan function has only values in $[0,\pi]$ if and only if the first argument is not negative, which is always true for the transverse momentum.

With this, I would like to stay with the current implementation, because it is slightly faster than the usage of arccos, especially in coordinate systems that provide direct access to the transverse momentum.

[mmikhasenko]

I see what you mean for the range, it's likely correct. I'd add a test for it.
For the speed, I'd surprised to see that gain, but could well be I do not have an intuition.

[mmikhasenko]

Confirm that the range is what I want: I've added the test for the ranges.
Fill free to merge if happy