Atan2.bas

 '*********************************************** 
 ' 
 'Atan2.bas by Nally + April 2000 
 'Released as open source 
 ' 
 'A function called ATAN2() is provided herein. 
 'ATAN2() takes two arguements: cartesian x and y 
 'coordinates. It returns an angle, phi, in'radians. 
 ' 
 'ATAN2() differs from ATN() in this regard: 
 'while ATN() only returns an angle between 
 '-pi/2 and +pi/2, ATAN2() will return any 
 'angle in the full circle. 
 ' 
 'The user should not call the function if both 
 'x and y = 0. This corresponds to a point at 
 'the origin of the coordinate system where 
 'the angle phi has no meaning. 
 ' 
 '*********************************************** 
 pi = 3.14159265 
 Print " " 
 Print "Note: Input real numbers for" 
 Print " x and y. Either x or y" 
 Print " or both must be non-zero." 
 Print " " 
 Print "** INPUT **" 
 Print " " 
 Input "x = "; x 
 Input "y = "; y 
 Print " " 
 Print "** OUTPUT **" 
 Print " " 
 phiRads = ATAN2(x, y) 
 phiDegs = 360 * (phiRads / (2 * pi)) 
 R = (x^2 + y^2)^(1/2) 
 Print "Cartesion Coordinates of Q....Q("; x; ", "; y; ")" 
 Print " " 
 Print "ATAN2 in radians.............."; phiRads 
 Print "ATAN2 in degrees.............."; phiDegs 
 Print "Distance to Q................."; R 
 Print " " 
 Print "Polar Coordinates of Q........Q("; phiRads; ", "; R;")" 
 
 End 
 Function ATAN2(x, y) 
 pi = 3.14159265 
 Result$ = "Undetermined" 
 If (x = 0) and (y > 0) Then 
 ATAN2 = pi / 2 
 Result$ = "Determined" 
 End If 
 If (x = 0) and (y < 0) Then 
 ATAN2 = 3 * pi / 2 
 Result$ = "Determined" 
 End If 
 If (x > 0) and (y = 0) Then 
 ATAN2 = 0 
 Result$ = "Determined" 
 End If 
 If (x < 0) and (y = 0) Then 
 ATAN2 = pi 
 Result$ = "Determined" 
 End If 
 If Result$ = "Determined" Then [End.of.function] 
 BaseAngle = Atn(abs(y)/abs(x)) 
 If (x > 0) and (y > 0) Then ATAN2 = BaseAngle 
 If (x < 0) and (y > 0) Then ATAN2 = pi - BaseAngle 
 If (x < 0) and (y < 0) Then ATAN2 = pi + BaseAngle 
 If (x > 0) and (y < 0) Then ATAN2 = 2*pi - BaseAngle 
 [End.of.function] 
 End Function