令 x=sint,dx costdt x=0,1=0x=l1=2 dx=sin-sin'i costdt -sm2h 0rdo=r4-k-小x-平dk π15π =π 1616 1010 令 x t dx tdt = = sin , cos 0, 0; 1, 2 x t x t  = = = = 1 2 2 2 2 2 0 0 x x dx t t tdt 1 sin 1 sin cos  − = −   2 2 0 1 sin 2 4 tdt  =  2 0 1 (1 s4 ) 8 co t dt  = −  16  = 2 D x d  2 1 2 2 2 2 0 0 = − − − x x dx x x dx 4 1   15 16 16   = − = 