Now, the point is that we have seen according to linear theory, sum of these two waves will simply be given by this sum of the two. Why? Because linear theory allows me to superpose waves. You see if for example, this is a solution the for problem phi 1, this is a solution for the problem phi 2, then we find out that basically, phi is a linear, the system is linear as well as… Therefore, phi 1 plus phi 2 can be added, superpose