FUNCTION ARCOS(X)
      implicit real*8 (a-h,o-z)
      include 'COMMON.GEO'
      IF (DABS(X).LT.1.0D0) GOTO 1
      ARCOS=PIPOL*(1.0d0-DSIGN(1.0D0,X))
      RETURN
    1 ARCOS=DACOS(X)
      RETURN
      END