二、勒让德函数的其他表达式

    
                                                                     
    
                                                                     

    

式中平面上的一条正向的简单闭曲线(图12.2),包围点是,但不包围点.

     (或当为整数)时,
       

        
                                          
                  
                                                            
        
        
                                                     
        

        

其中积分路线见图12.3.时,