练习16 一.2.z=∫( e sin y,"), az e sin y (f,2) f1· e sin y-f2 J a 2 一.5.z=-∫(xy)+yq(x+y), z ar +2ff(xy)+f(xy) y+ yo(x+y), 02z axa 2f() x+f(xy) xy+f(xy) +o(x+y)+yo(+y)=o+yo+f")练习1.6 一. 2. ( sin , ), x y z f e y x =           − =   2 1 2 sin ( , ) x y e y f f x z x sin . 1 2 2 x y f e y f x =  −  一. 5. ( ) ( ), 1 f xy y x y x z = +  + ( ) ( ), 1 ( ) 1 2 f xy y y x y x f xy x x z = − +   +  +    ( ) 1 ( ) 1 ( ) 1 2 2 f xy x f xy xy x f xy x x y x z = −   +   +     +(x + y) + y(x + y) =  + y( + f )