[微分] 89清大經濟
2 2
Let f:| R --> | R be differentiable . Given u=(3/5,4/5), v=(4/5,-3/5)
2 ' 2 ' 2
prove that | gradient f | = |f_u| + |f_v|
' '
where f_u and f_v are the directional derivative of f in the direction
of u and v
這題不知道該怎樣證 連第一步要怎樣進行都無頭緒
請版友解題了 謝謝:)
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