我假設你沒有f,g,h的表達式,但是你想要用f,g,h的導數表示組合的導數。
你總是可以減少問題的單值函數,通過使用像f[x_,y_] := {f1[x,y],f2[x,y],f3[x,y]}
例如一個定義:
f[x_, y_] := Through[{f1, f2, f3}[{x, y}]]
g[x_, y_, z_] := Through[{g1, g2, g3}[{x, y, z}]]
D[h @@ g @@ f[x, y], x]
結果:
(Derivative[{1, 0}][f3][{x, y}]*Derivative[{0, 0, 1}][g3][{f1[{x, y}], f2[{x, y}], f3[{x, y}]}] +
Derivative[{1, 0}][f2][{x, y}]*Derivative[{0, 1, 0}][g3][{f1[{x, y}], f2[{x, y}], f3[{x, y}]}] +
Derivative[{1, 0}][f1][{x, y}]*Derivative[{1, 0, 0}][g3][{f1[{x, y}], f2[{x, y}], f3[{x, y}]}])*
Derivative[0, 0, 1][h][g1[{f1[{x, y}], f2[{x, y}], f3[{x, y}]}], g2[{f1[{x, y}], f2[{x, y}], f3[{x, y}]}],
g3[{f1[{x, y}], f2[{x, y}], f3[{x, y}]}]] +
(Derivative[{1, 0}][f3][{x, y}]*Derivative[{0, 0, 1}][g2][{f1[{x, y}], f2[{x, y}], f3[{x, y}]}] +
Derivative[{1, 0}][f2][{x, y}]*Derivative[{0, 1, 0}][g2][{f1[{x, y}], f2[{x, y}], f3[{x, y}]}] +
Derivative[{1, 0}][f1][{x, y}]*Derivative[{1, 0, 0}][g2][{f1[{x, y}], f2[{x, y}], f3[{x, y}]}])*
Derivative[0, 1, 0][h][g1[{f1[{x, y}], f2[{x, y}], f3[{x, y}]}], g2[{f1[{x, y}], f2[{x, y}], f3[{x, y}]}],
g3[{f1[{x, y}], f2[{x, y}], f3[{x, y}]}]] +
(Derivative[{1, 0}][f3][{x, y}]*Derivative[{0, 0, 1}][g1][{f1[{x, y}], f2[{x, y}], f3[{x, y}]}] +
Derivative[{1, 0}][f2][{x, y}]*Derivative[{0, 1, 0}][g1][{f1[{x, y}], f2[{x, y}], f3[{x, y}]}] +
Derivative[{1, 0}][f1][{x, y}]*Derivative[{1, 0, 0}][g1][{f1[{x, y}], f2[{x, y}], f3[{x, y}]}])*
Derivative[1, 0, 0][h][g1[{f1[{x, y}], f2[{x, y}], f3[{x, y}]}], g2[{f1[{x, y}], f2[{x, y}], f3[{x, y}]}],
g3[{f1[{x, y}], f2[{x, y}], f3[{x, y}]}]]