[微積] 可微分性
各位高手大家好
我對於"可微分性"的定義一直搞不太清楚
我在看的書是有寫
多變數函數之可微分定義:
n m n m
設f:D R⊆R —>R 的函數且若存在一從R 映至R 的線性函數
Df(x_0) , 其中x_0∈D滿足
||f(x_0+Δx)-f(x_0)-Df(x_0)Δx||
lim = ---------------------------------- = 0
Δx->0 ||Δx||
,則稱函數f在點x_0∈D是可微分
所以是每次遇到題目都要用這個定義做嗎?
還有他這裡說的是在點x_0,那如果只是問可不可微呢?
像是
f(x) ={ (x^2)sin(1/x) , x ≠ 0
{
{ 0 , x = 0
或是
2 2
f:R —>R 定義為
2
f(x,y) = (φ(x,y),Ψ(x,y)) , for all (x,y)∈R
其中φ(x,y)=x^2y^3 且 Ψ(x,y)=x*exp(y^2) ,
2
for all (x,y)∈R 是否為可微分函數
只要告訴我一點概念或方向就好
謝謝!!!
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