a=200;//leangth of cross section along x-axis,given in mm
b=300;//leangth of cross section along y-axis,given in mm
tx=25;//thickness along x-axis,given in mm
ty=20;//thickness along y-axis,given in mm
M=100*10^6;//bending moment,given in N.mm
th=30;//inclination of plane of bending moment,given in degrees
theta=th*%pi/180;//th in radians