1. it is given that cos(42'-Θ)tan(42'-Θ)=cos(2Θ+18') , where Θ is an acute angle .
a) find Θ by using the trigonometric identities
b) using the result obtained in(a) , find the value of 3cosΘ sin(15'-Θ) tan 2Θ
2.a) prove that 1-cos Θ/ 1+cos Θ = (1-cosΘ/sinΘ)^2 .
plz help me T_T 大大感激xd
請詳細說明，不要只寫答案＞＿＜ thank you :)))))
'= 度 ， /＝over
(20點)中三trigonometric relations
2014-04-21 9:04 am
回答 (2)
2014-04-21 7:16 pm
✔ 最佳答案
The answer is as follows :圖片參考：https://s.yimg.com/lo/api/res/1.2/Tnct6Ekkjsxm4geWwzoLNQ--/YXBwaWQ9dHdhbnN3ZXJzO3E9ODU-/http://dc313.4shared.com/img/ZSF-RJ7Zba/s7/145824529f0/2014-04-21A.png?async&rand=0.5869872094120142
http://dc313.4shared.com/img/ZSF-RJ7Zba/s7/145824529f0/2014-04-21A.png?async&rand=0.5869872094120142
2014-04-21 11:19:38 補充：
2. (b)
若 F.3 未學過 15° 的 special angle，則直接計算便可：
3 cos30° sin(-15°) tan60°
= 3 cos30° (-sin15°) tan60°
= -1.165
參考: pingshek, pingshek
2014-04-21 6:20 pm
中三應該未學compound angle, 1b 會不會是打錯了題目，應該是
find the value of 3 cosΘ sin(15'+Θ) tan 2Θ
find the value of 3 cosΘ sin(15'+Θ) tan 2Θ
收錄日期: 2021-04-30 16:50:36
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20140421000051KK00004