Int E0 Fn 001A  - Pcrobots V1.41 - "l_atan" - Get Angle Given Scaled Tang  [g]

   AX = 001Ah
   BX:CX = 100000*tangent of an angle

Return: AX = angle (-90 to +90 degrees)

See Also: AX=0017h,AX=0018h,AX=0019h