egin{equation}
label{equ1} A = Sleft( {egin{array}{*{20}{c}}
{{E_r}}&0 \
0&0
end{array}}
ight)T
end{equation}
eqref{equ1}
egin{equation}
label{equ1} A = Sleft( {egin{array}{*{20}{c}}
{{E_r}}&0 \
0&0
end{array}}
ight)T
end{equation}
eqref{equ1}