So, now supposing I assumed all these energies coming from direction 1, then my two-dimensional thing would have been 100 unit, but what we do is that, we say this 100 unit is spread there is 100 unit this would be hundred unit coming all waves in this direction. But I am going to say that this is equivalent to 80 coming from here, say 60 coming from here say, 20 coming from here, 5 coming from here, 2 here like that, so that the sum of this 60, 20, 5, 2 etcetera will become equal to 100 this is called directional spreading (Refer Slide Time 24.17). Now by doing this formula, we find out an S theta where this sum becomes remains 100 I give better example of of this here, see this book.