Imatan-func
The Imatan(z) function returns the inverse tangent of complex value z. Values returned are in radians, degree or gradian, depending on the setting of system.math.angularunits object property (which can also be set in the Options dialog box opened from menu Preference: Options).
complex atan(complex z)
z
Returns inverse tangent of complex z.
complex vv=3+4i; Imatan(vv)=; Imatan(vv)=1.4483069952315+0.15899719168i
asin, acos, acot, asec, acsc