Consider the displacement field: u1 = k(2x 2 1 + x1x2), u2 = kx2 2 , u3 = 0, k = 10−4 (2) (a) find the elongation per unit length and the change of angles between two infinitesimal vectors v = dx1e1 and w = dx2e2 that emanate from a particle with position vector x = e1 + e2. (b) sketch the deformed positions of these two vectors.