over the entire cross
section
ii) The bending moment produces
a linearly varying stress 
with compression on the upper part of the
beam and tension on the lower part.
iii) Thus, the equation for the combined stresses is
over the entire cross
section
ii) The bending moment produces
a linearly varying stress with compression on the upper part of the
beam and tension on the lower part.
iii) Thus, the equation for the combined stresses is