subroutine Pre_xt1(x12, x1,x2,x3) ! x12 = xt1(x1,x2,x3)

    complex, intent(in)     :: x1,x2,x3
    complex, intent(out)    :: x12

    x12 = x1+(x2*x3)/(x2+x3)

end subroutine Pre_xt1
subroutine Pre_vc(V,current,v1,v2,P,xt1) ! V,current = vc(v1,v2,P,xt1)
    real, intent(in)     ::  v1,v2,P
    complex, intent(in)     :: xt1
    complex, intent(out)    :: V,current
    real :: delR,delD,a,b
    delR = asin(P*ABS(xt1)/ABS(v1)*ABS(v2))
    delD = delR*180/ 3.1415927
    a = v1*cos(DelR)
    b = v1*sin(DelR)
    V = CMPLX(a,b)
    current = (V-v2)/xt1

end subroutine Pre_vc
subroutine Pre_PM(Pemax,Eg,V,v2,xg,xt1,current) ! Pemax,Eg = PM(V,v2,xg,xt1,current)
    real, intent(in)     :: v2
    complex, intent(in)     :: xg,xt1,current,V
    complex, intent(out)     :: Eg
    real, intent(out)     :: Pemax

    Eg = (current*xg)+V
    Pemax = (ABS(Eg)*v2)/(abs(xg)+abs(xt1))

end subroutine Pre_PM
subroutine duringpost(Pd,Pp,x1,x2,x3,xg,E1,E2) ! Pd,Pp = duringpost(x1,x2,x3,xg,E1,E2)
    implicit none
    complex, intent(in) :: x1,x2,x3,xg
    complex, intent(in) :: E1,E2
    complex, intent(out)     :: Pd,Pp
    real :: y12,y13,y32,y33
    y13 = abs(1/(xg+x1))
    y32 = abs(1/x2)
    y33 = -abs((1/(x1+xg))+(1/x2)+(1/(x3/2)))
    y12 = -(y13*y32)/y33

    Pd = abs(E1)*abs(E2)*y12
    Pp = abs(E1)*abs(E2)/(abs(xg+x1+x2))

end subroutine duringpost