if A,B,C are the angles of a triangle, proved that
a) tanA = -tan(B+C)
b)cosA/2 = sin(B+C)/2
收錄日期: 2021-04-25 16:58:58
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070418000051KK03676