Code: Select all
' demo_atan3.bas
' June 24, 2015
' demonstrates how to intereact with the ATAN3 subroutine
dtr = PI / 180.0
rtd = 180.0 / PI
angle_deg = 222.25678
' convert angle to radians
angle_rad = dtr * angle_deg
' compute sin and cosine of angle
a = sin(angle_rad)
b = cos(angle_rad)
' call four quadrant inverse tangent
GOSUB ATAN3:
' print results
print " "
print "user-defined angle = ", angle_deg, " degrees"
print " "
print "a = ", a
print "b = ", b
print " "
print "angle from ATAN3 = ", rtd * c, " degrees"
END
ATAN3:
' four quadrant inverse tangent function
' input
' a = sine of angle
' b = cosine of angle
' output
' c = angle (0 =< c <= 2 * pi : radians)
'''''''''''''''''''''''''''''''''''''''''
pidiv2 = PI / 2.0
x = a
GOSUB SIGN:
sgn_a = sgn
x = b
GOSUB SIGN:
sgn_b = sgn
IF (ABS(a) < 1.0e-10) THEN
c = (1.0 - sgn_b) * pidiv2
RETURN
ELSE
c = (2.0 - sgn_a) * pidiv2
ENDIF
IF (ABS(b) < 1.0e-10) THEN
RETURN
ELSE
c = c + sgn_a * sgn_b * (ABS(ATAN(a / b)) - pidiv2)
ENDIF
RETURN
'''''''''''''''
'''''''''''''''
SIGN:
' sign of a variable subroutine
' input
' x = argument
' output
' sgn = sign of x
''''''''''''''''''
IF (x > 0.0) THEN
sgn = 1.0
ENDIF
IF (abs(x) <= 1.0e-12) THEN
sgn = 0.0
ENDIF
IF (x < 0.0) THEN
sgn = -1.0
ENDIF
RETURN