The engineering strain matrix at a particular point in a structure is I [e]ong = Ex Yay Yx Yyr Ey Yyz LYzx y zy Ez To www 0 2 2 -2 x 10-4 0 3 -2 -1 Determine the engineering strain matrix relative to a coordinate system de- fined by first rotating the ryz coordinate system -30 about the x axis, then rotating 40 about the new y axis. determine the principal strains and their corresponding di- rectional cosines that indicate their directions.