and 





-. dt 



i>i 



- n 1^-^3 1^ 



we have 



iTTo. 



r 



4_ ^3 dp 

 LA ^f d\r\ 



Cosh if?Qh 



4- 



-f an 







- r 



i -h 



hcosliVr^a 



CosV^^Qh 



19 



