18. Strain at a point is such that Ea. = = 0, ^ = -0.001, = 0.006, and evz = ^ = 0. Note:

You need not solve the eigen value problem for this question.

(a) Show that n1 = i + j and n2 = —i + j are principal directions of strain at this point.

(b) What is the third principal direction?

(c) Compute the three principal strains.