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SUBROUTINE AZSQRT(AR, AI, BR, BI)
C***BEGIN PROLOGUE AZSQRT
C***REFER TO ZBESH,ZBESI,ZBESJ,ZBESK,ZBESY,ZAIRY,ZBIRY
C
C DOUBLE PRECISION COMPLEX SQUARE ROOT, B=CSQRT(A)
C
C***ROUTINES CALLED AZABS
C***END PROLOGUE AZSQRT
DOUBLE PRECISION AR, AI, BR, BI, ZM, DTHETA, DPI, DRT
DOUBLE PRECISION AZABS
DATA DRT , DPI / 7.071067811865475244008443621D-1,
1 3.141592653589793238462643383D+0/
ZM = AZABS(AR,AI)
ZM = DSQRT(ZM)
IF (AR.EQ.0.0D+0) GO TO 10
IF (AI.EQ.0.0D+0) GO TO 20
DTHETA = DATAN(AI/AR)
IF (DTHETA.LE.0.0D+0) GO TO 40
IF (AR.LT.0.0D+0) DTHETA = DTHETA - DPI
GO TO 50
10 IF (AI.GT.0.0D+0) GO TO 60
IF (AI.LT.0.0D+0) GO TO 70
BR = 0.0D+0
BI = 0.0D+0
RETURN
20 IF (AR.GT.0.0D+0) GO TO 30
BR = 0.0D+0
BI = DSQRT(DABS(AR))
RETURN
30 BR = DSQRT(AR)
BI = 0.0D+0
RETURN
40 IF (AR.LT.0.0D+0) DTHETA = DTHETA + DPI
50 DTHETA = DTHETA*0.5D+0
BR = ZM*DCOS(DTHETA)
BI = ZM*DSIN(DTHETA)
RETURN
60 BR = ZM*DRT
BI = ZM*DRT
RETURN
70 BR = ZM*DRT
BI = -ZM*DRT
RETURN
END
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