Two infinitesimal lines dL 1 and dL 2 within a material are parallel to the and y axes in a…

Two infinitesimal lines dL1 and dL2
within a material are parallel to the  and y axes in a reference
state (Fig. (a)). After a motion and deformation of the material, dL’1
points in the direction of the unit vector e1 = 0.717i
+ 0.535j – 0.447k, and dL’ 2 points in the
direction of the unit vector e2 = 0.514i + 0.686j
+ 0.514k (Fig. (b)). What is the shear strain referred to the directions
dL1 and dL2?