c $Header: /usr/people/flittner/radtran/tomrad/pv2.2/src/RCS/quadcoe.f,v 2.22 2000/08/30 16:38:09 flittner Exp $
        subroutine quadcoe(x,c)
c
c compute the coefficients of quad. function tabulated at 3 points given
c the pts where it is tabulated (the x vector)
c
c return coef. array such that 
c f(x)=c(0,0)*f(x(0))+c(1,0)*f(x(1))+c(2,0)*f(x(2))
c     +(c(0,1)*f(x(0))+c(1,1)*f(x(1))+c(2,1)*f(x(2)))*x
c     +(c(0,2)*f(x(0))+c(1,2)*f(x(1))+c(2,2)*f(x(2)))*x*x
c
c or f(x)=
c     [f(x0),f(x1),f(x2)] [c00 c01 c02] |1  |
c                        *|c10 c11 c12|*|x  |
c                         [c20 c21 c22] |x*x|
c
        implicit none
c the rcs revision #
      character*20 rcsrev
      parameter (rcsrev='$Revision: 2.22 $')
c passed
        real*8 c(3,3),x(3)
c local
        real*8 a(3)
c
        a(1)=x(3)-x(2)
        a(2)=x(3)-x(1)
        a(3)=x(2)-x(1)
c
c constant term
        c(1,1)=x(2)*x(3)/a(2)/a(3)
        c(2,1)=-x(1)*x(3)/a(1)/a(3)
        c(3,1)=x(1)*x(2)/a(1)/a(2)
c
c linear term
        c(1,2)=-(x(3)+x(2))/a(2)/a(3)
        c(2,2)=(x(3)+x(1))/a(1)/a(3)
        c(3,2)=-(x(1)+x(2))/a(1)/a(2)
c
c quad term
        c(1,3)=1.0/a(2)/a(3)
        c(2,3)=-1.0/a(1)/a(3)
        c(3,3)=1.0/a(1)/a(2)
        return
        end