Re: [線代] 線代的證明題
※ 引述《SS327 (土豆人)》之銘言:
: t t
: 題目:A為方陣,若A A=AA則A=A
: 請問怎麼證明阿?
假定A是實數方陣, 複矩陣^t要是Hermitian conjugate.
Let '=^t, then A'A=AA=A'A'.
Recall that a real matrix M=0 iff Tr(MM')=0.
Thus, to show that A=A', we only need to prove Tr(KK')=0, where K=A-A'.
Note that KK'=AA-A'A-AA'+A'A' = A'A-AA'
Clearly, Tr(KK')=0 as Tr(A'A)=Tr(AA').
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◆ From: 76.94.119.209
※ 編輯: Sfly 來自: 76.94.119.209 (02/08 06:20)
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