1. The problem statement, all variables and given/known data 2. Relevant equations None really. 3. The attempt at a solution I know that to make a wave completely destructive to the original I'd have to add pi, so I tried the answer 0+pi*n, which was wrong. I also tried 0 + 3pi*n, which would shift the wave to another destructive position but that wasn't correct either. Would any of you guys know what I'm doing wrong or overlooking? Thanks a lot! I'm thinking that it may be pi + 2*pi*n, but I want to get some opinions before I try submitting.