8. Let
f(x, y) = x + sin(x + 2y).
Find the unit vector in the direction in which f increases most rapidly at the point (0, 0) and give the rate of change of f in that direction.
詳解 (共 1 筆)
助人為本
詳解 #7381891
這題的話用梯度來解
梯度向量就是把x和y做偏微分,然後把它湊成一個向量

然後我們把點(0,0)代入,可以得到梯度向量為(2,2)
然後題目要問變化率,就是這個梯度向量(長度)大小

再來題目要求單位向量,就是向量分之長度,不過分子要是1
