Re: Lagrange
※ 引述《yeyuiang (color0619)》之銘言:
: 用Lagrange求
: find the minimum value of f(x,y)=x^2-y^2 subject to
: the constraint x^2+y^2=4
: 我算過 可是算出來怪怪的= =+....
: fx出來的朗打=1
: 但fy出來的朗打= - 1
: 有請高手了!!!!謝
高中解法 有錯請指教
let x=2cosk
y=2sink
f(k)=4(cosk)^2-4(sink)^2
=4[1-(sink)^2]-4(sink)^2
=4-8(sink)^2 (sink)^2最大是1 最小是0
so min=-4
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