(*         PRINCIPAL STRESSES-2 D          *)

(* This file calculates the two in-plane principal stresses
from equation (1.11).
To use this file in cylindrical polar coordinates,uncomment the two lines below and comment the present expressions for σ1,σ2. *)

(* σ1=(σrr+σθθ)/2+Sqrt[((σrr-σθθ)/2)^2+σrθ^2];
σ2=(σrr+σθθ)/2-Sqrt[((σrr-σθθ)/2)^2+σrθ^2]; *)



σ1:=(σxx+σyy)/2+Sqrt[((σxx-σyy)/2)^2+σxy^2]
σ2:=(σxx+σyy)/2+Sqrt[((σxx-σyy)/2)^2+σxy^2]