Re: [微分] 微分證明
※ 引述《qscf753 (夜月風翔)》之銘言：
: ※ 引述《BaBi (迅雷不及掩耳盜鈴)》之銘言：
: : d d -1
: : ---- (secx) = ---- (cos x)
: : dx dx
: : -2
: : = (-1)(cos x)(-sinx)
: ^^^^^^^^^^^^^^^^^^^^^^^
: 請問這段怎麼來的呢 我知道是chain rule
: -1 -2
: 但是有點搞混...cos x微分過一次變成cos x 後面怎麼又微一次變成-sinx?
-1
let u = cos(x), y = sec(x) = u
d d du d -1 d
---(y) = ---(y) * ---- = ---( u ) * --- [cos(x)]
dx du dx du dx
-2 -2
= -u * [-sin(x)] = - (cosx) * [-sinx]
--
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