2 Derive the equation de = 3 d using eqn (3-39) and then derive the eqn (3-47) equations for principal plastic strain increments. d = di d2 3 = = -[(de de) + (d2 de) + (d - d) ] 2 (3-39) d d d - 01 02 - - 1 2 (02 + 03)] de, - 14/410, - 1/1 (0 + 02 ) ] = 03 2 (3-47)