Please go to http://aerodrive.twghwfns.edu.hk/~4s123/Q15.JPG and find the figure.
The question:In triangle ABC.D is the mid-point of BC.By considering b and using the Cosine Law,prove that AB^2+AC^2=2AD^2+2CD^2.
Thx~~~~
A.Maths Problem(Solution of triangles and its application)
2006-12-30 7:37 am
回答 (1)
2006-12-30 8:12 am
✔ 最佳答案
consider AB,ACAB^2=AD^2+BD^2-2(AD)(BD)cos(180-b)
AB^2=AD^2+BD^2+2(AD)(BD)cosb
AC^2=AD^2+CD^2-2(AD)(CD)cosb
AB^2+AC^2
=AD^2+BD^2+2(AD)(BD)cosb+AD^2+CD^2-2(AD)(CD)cosb
=2AD^2+2CD^2 (since CD=BD)
收錄日期: 2021-04-25 16:49:06
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20061229000051KK03998