2兀 x+ 根据椭圆的对称性知 S2 (sin扩)+(1+a人cos 0 2*V1+a cos2tdt 21v1+acos xd=S, 故原结论成立( ) ( ) , 2 0 2 2 2 s x y dt   =  +  根据椭圆的对称性知 s ( t) ( a )( t) dt   = + + 0 2 2 2 2 2 sin 1 cos a xdx   = + 0 2 2 2 1 cos , 1 = s 故原结论成立. a tdt   = + 0 2 2 2 1 cos