6. Write an expression that could be used to determine the strain tensor in a certain coordinate system if the stress tensor in that same coordinate system is known. First do this using the i=1,2,3 notation and then do it with the i=1,2,3,4,5,6 notation. Next, write the specific equation, in expanded form, that you would use for determining the normal strain in the y-direction (do this in the 1-3 notation and again in the 1-6 notation)