For a bidirectionally reinforced fiber reinforced composite laminate the fibers are oriented at
600
and 1200

, respectively, with respect to the x1 axis in un-deformed configuration. If

the laminate is subjected to a deformation gradient given by y1=x1+t x2

, y2=(1+t) x2
then a) establish the stretch in these fibers as a function of t, b) for two fibers that are oriented at
600
and 1200

, establish the equation relating the angle between the fibers with time.