,=-EorCos0+2Br(m+Pm(cos 0) d2=∑APm(cosO) F三m Eoacos 6+∑B -(m+1) P (cos Aa"P(cos FE cos8-8(m+12Bma-mtpm(cos 0 6m∑41am0Pm(cos)( ) ( ) ( ) ( ) ( ) ( ) ( ) ( 1) 1 0 2 ( 1) 0 ( 2) 0 1 0 cos cos cos cos cos cos cos 1 cos cos m m m m m m m m m m m m m m m m m m m m m m m m E r B r P A r P r a E a B a P A a P E m B a P m A a P              − +    − +  − +  −  = − +  = =  − + =     − − +    =       