證明sin5X/sinX - cos5X/sinX = 4cos2X?
回答 (1)
2016-11-05 11:33 am
✔ 最佳答案
證明Sin(5x)/sinx–Cos(5x)/Cosx=4Cos(2x)?Sol
A=Sin(5x)/Sinx–Cos(5x)/Cosx
ASinxCosx
=Sin(5x)Cosx－Cos(5x)Sinx
=Sin(5x－x)
=Sin(4x)
=Sin(2x+2x)
=2Sin(2x)Cos(2x)
A=2Sin(2x)Cos(2x)/(SinxCosx)
=4Sin(2x)Cos(2x)/(2SinxCosx)
=4Sin(2x)Cos(2x)/Sin(2x)
=4Cos(2x)
收錄日期: 2021-04-18 15:45:50
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20161105031627AACrkzH