A)Show that (sin B - cos B)^2 +(sin C - cos C)^2 - (sin A - cos A)^2
=1 - (sin2B+sin2C -sin2A).
B) If A+B+C=180,deduce, from A),that
(Sin B - cos B)^2 + (sin C - cos C)^2 - (sin A -cos A)^2
=1 - 4sinAcosBcosC.
Furthermore, if A = 90, find the greatest value of cosBcosC.
三角學問題HKHLE1985
2013-03-30 7:01 pm
回答 (2)
2013-03-30 8:13 pm
✔ 最佳答案
--------------------------------------------------------------------------------------------------圖片參考：http://imgcld.yimg.com/8/n/HA05107138/o/20130330121130.jpg
圖片參考：http://imgcld.yimg.com/8/n/HA05107138/o/20130330121318.jpg
2013-03-30 8:16 pm
收錄日期: 2021-04-13 19:23:46
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20130330000051KK00085