※ 引述《hero010188 (我是海賊王)》之銘言：
: https://i.imgur.com/dcLgVqB.png
: 想不到怎麼寫比較好 QQ 感謝
平面向量a, b所張面積 = △ = |det(a, b)|
△ = |det(5a, 3b - 4c)|
= |15det(a, b) - 20det(a, c)|
=> | 15|det(a, b)| - 20|det(a, c)|| <= △ <= 15|det(a, b)| + 20|det(a, c)|
=> | 15 - 40 | <= △ <= 15 + 40
=> 25 <= △ <= 55
det(a, b)和det(a, c)異號時△ = 55
det(a, b)和det(a, c)同號時△ = 25
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※ 編輯: Honor1984 (61.231.17.176 臺灣), 01/14/2025 11:35:05