求 sin19∘cos79∘−sin71∘cos11∘ =?
回答 (3)
2017-04-03 6:16 pm
✔ 最佳答案
SolSin19度Cos79度－Sin71度Cos11度
= Sin19度Cos79度－Cos19度Sin79度
=Sin(19度－79度)
=Sin(－60度)
=－√3/2
2017-04-06 8:55 pm
-0.866025403
2017-04-03 12:42 pm
sin19∘cos79∘=
1/2(sin(19+79)+sin(19-79))=1/2(sin(98)+sin(-60))=1/2(cos(8)-sin(60))
sin71∘cos11∘ =
1/2(sin(71+11)+sin(79-11))=1/2(sin(82)+sin(60))=1/2(cos(8)+sin(60))
sin19∘cos79∘−sin71∘cos11∘ = 1/2(cos(8)-sin(60))- 1/2(cos(8)+sin(60)) =
-sin(60)=(3^1/2)/2=-0.866
1/2(sin(19+79)+sin(19-79))=1/2(sin(98)+sin(-60))=1/2(cos(8)-sin(60))
sin71∘cos11∘ =
1/2(sin(71+11)+sin(79-11))=1/2(sin(82)+sin(60))=1/2(cos(8)+sin(60))
sin19∘cos79∘−sin71∘cos11∘ = 1/2(cos(8)-sin(60))- 1/2(cos(8)+sin(60)) =
-sin(60)=(3^1/2)/2=-0.866
收錄日期: 2021-04-18 16:10:41
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20170403031625AAH12jp