S1=60;//stress parallel to the x reference axis,given,in N/mm^2
S2=40;//stress perpendicular to the x reference axis,given,in N/mm^2
theta=45*(%pi/180);//given
El=150000;//given,in N/mm^2
Et=90000;//given,in N/mm^2
Glt=5000;//given,in N/mm^2
vlt=0.3;//given