function [ output_args,this ] = equ( this )
%EQU Summary of this function goes here
%   Detailed explanation goes here
PDi=this.PDi;
QDi=this.QDi;
Volt0=this.Volt0;
Angel=this.Angel;
r=this.r;
c=this.c;
PG=this.PG;
QG=this.QG;
PD=x(1:length(PDi));
QD=x(length(PDi)+1:length(PDi)+length(QDi));
Volt=x(length(PDi)+length(QDi)+1:length(PDi)+length(QDi)+length(Volt0));
VAngel=x(length(PDi)+length(QDi)+length(Volt0):end);
PD_=zeros(PD,length(Volt0));
QD_=zeros(QD,length(Volt0));
PD_(PDi)=PD;
QD_(QDi)=QD;
busNum=length(Volt0);
VMatrix=sparse(r,c,VAngel(r)-VAngel(c)-Angel,busNum,busNum);
dP=PG-PD_-diag(Volt)*(Y.*cos(VMatrix))*Volt;
dQ=QG-QD_-diag(Volt)*(Y.*spfun(@sin,VMatrix))*Volt;
output_args=[dP;dQ];
this.gle=ze
end