16 



The height from trough to crest is 2a and the wave is symmetrical 

 about the crests. The mean elevation between trough and crest is 



ira 



-J- above the still water level y=0. The equation for the wave 



CO 



kJ 



O 

 K 

 Q. 



U 



> 



I 



li. 

 O 



z 

 o 



CO 



tr 



o 

 o 



o 



form is also sometimes expressed as 



L 



2tx ira^ 



Airx 



(13c) 



Here y' is the distance above or below a horizontal line at midheight 



