Re: [問題] 數學分點公式(高一)
看板juniorhigh作者kevin051118 (Kevin凱文)時間13年前 (2010/09/18 20:39)推噓36(36推 0噓 27→)留言63則, 13人參與討論串2/3 (看更多)
※ 引述《tyler1111 (小昊)》之銘言:
: 雖然是高一題目,不過我還是喜歡溫馨的國中版阿~~
: ---以下題目開始
: 平面上有 A(3,4). B(5,-2). C(x,y)三點共線,
: 且B在線段AC上,若AB=2BC,求C點座標。
: ---題目結束
: 我知道這個可以用內分點公式算....
: 不過我想知道能不能不要用分點公式算?
: 另外二維的分點公式是怎樣證出來的?
(3,4) (5,-2) (x,y)
──●───────●────●────
A B C
A → B = (5-3 , -2-4) = (2 , -6)
∵AB=2BC
∴B → C = (1 , -3) = (x-5 , y+2)
∴ x= 6 , y= -5
驗算後應該沒錯
話說有人可以跟我說這是什麼方法嗎 囧 變成反射動作 ( ̄□ ̄|||)a
求證: c = (na+mb)/(n+m)
m n
──●───────●────●────
A C B
(c-a):(b-c) =m:n
m(b-c)=n(c-a)
mb-mc=nc-na
nc+mc=mb+na
c(n+m)=mb+na
c= (na+mb)/(n+m)
得證
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◆ From: 114.47.147.3
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※ 編輯: kevin051118 來自: 114.47.147.3 (09/18 20:59)
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