clear
clc
syms T11 T12 T21 T22;
syms V1 V2;
syms Y11 Y12 Y21 Y22;
yP=ones(1,2);
AngleIJ=[T11,T12;T21,T22];
Volt=[V1,V2];
Y=[Y11,Y12;Y21,Y22];
t1=-diag(Y.*cos(AngleIJ')*diag(Volt)*yP');
t2=diag(diag(Volt)*yP')*Y.*cos(AngleIJ);
t3=(t1+t2)*diag(Volt);
t4=-(diag(Y.*cos(AngleIJ)*Volt') -diag(Volt)*Y.*cos(AngleIJ') )*diag(diag(Volt)*yP');
ddPdTdT=t1+t2+t3+t4