f(cos kIs k ∫ao+∑{acos k L+b. sinTx Z xX cos kre dE hIs CoS 了os knx COS ds+ +△∫ 6. sin i coS nIS knox kcos2k丌x k k 1+cOs 2 S, 20 1 0 1 1 2 1 ( ) cos 1 [ { cos sin }]cos 1 cos 1 cos cos 1 sin cos 1 1 1 cos [1 cos 2 2 l k l k l k k l k k l l k l k l k k l k l k k l k k l k k k a f d l l k x k x k a a b d l l l l k a d l l k x n a d l l l k x n b d l l l k x k x a d a l l l l                          −  − = −  − =  − = − = = = + + = + + + = = +          ] 1 1 1 2 2 2 l l l k k k l k k k d l a a d a l l      − − = = = =  