Note that atan2 function correctly recovers the angle alpha from X and Y in all cases. The normal arctan function only works on half of the circle, and there's a singularity at X=0.
11
Expression 12: alpha Subscript, 0 , Baseline equals "A" left parenthesis, "Y" , "X" , right parenthesisα0=AY,X
equals=
0.4 70.47
12
Expression 13: alpha Subscript, 1 , Baseline equals arc tangent left parenthesis, StartFraction, "Y" Over "X" , EndFraction , right parenthesisα1=arctanYX