 Now first tell me how a wave equation looks like, y is equal to, that is SHM equation omega t plus 5, equation looks like that, okay just plus pi right away if you put it becomes cross. So we will be consistent with the book, so we will use that on A. The second way is minus omega 2 t plus 5. Now when these two waves, this is 5, so this will become frequency, so phase wave for which y will become 0 no matter what time it is. When 5 then constructively different will happen, so 5 is equal to 2 and 5, so if the phase is the second different, constructively different. I have to remember second case, how to do the second and how to do the third wave, one phase will be 3 to the omega t, what omega t minus 5 by 2 minus 5 by 2. No omega, this goes. Suppose, we cancel same thing in the second, finally we will come off, omega t minus 5 by 2 minus 5 by 2. So this is how this square n becomes 1.