9.曲线 二co2布=处的切线方程 y=sint dx dt =-2sin 2t, dt dy cost dx -2sin 2t 4sint 2 4 (x-0 √W2x+4y-22=0 2x y + − = 4 2 2 0 cos 2 sin 4 x t t y t  =   =  = 9.曲线 在 处的切线方程 2sin 2 , cos , dx dy t t dt dt = − = 4 2 t 4 dy dx  = = − cos 1 , 2sin 2 4sin dy t dx t t = = − − 2 , 0, 2 t = x y 4  = = 2 2 ( 0) 2 4 y x − = − −