我想問一條數....
若A+B+C=180度, PROOF cos^2A+cos^2B-cos^2C-1= -2sinAsinBcosC
math....急
2007-02-21 11:35 pm
回答 (1)
2007-02-21 11:54 pm
✔ 最佳答案
Please find the deductions as follows:圖片參考：http://i117.photobucket.com/albums/o61/billy_hywung/Maths/Crazytrigo8.jpg
參考: My Maths knowledge
收錄日期: 2021-04-13 14:46:34
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070221000051KK02762