please prove
sin2a+sin2b+sin2c=4sinasinbsinc
please help me prove sin
2011-06-12 6:54 am
回答 (1)
2011-06-12 6:58 am
✔ 最佳答案
sin2A + sin2B + sin2C = 2sin(A + B)cos(A - B) +2sinCcosC= 2sinCcos(A - B) + 2sinC(-cos(A + B))= 2sinC[cos(A - B) - cos(A + B)]= 4sinAsinBsinC
收錄日期: 2021-04-13 18:01:59
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20110611000051KK01266