1)sin^2 400° +cos^2 220°+tan^2 315°=?
我知道ans係2...但係我想問點計出黎
2) simiplied 1/(2√3+ √2)=?
兩題中五數學問題
2007-04-26 6:16 am
回答 (1)
2007-04-27 8:52 am
✔ 最佳答案
1)sin^2 400° +cos^2 220°+tan^2 315°
=sin^2 (360°+40°) +cos^2 (180°+40°)+tan^2 (360°-45°)
=sin^2 40° +cos^2 40°+tan^2 45°
=1+1
=2
2)
1/(2√3+ √2)
=1/(2√3+ √2)*[(2√3- √2)/(2√3- √2)]
=(2√3- √2)/10 [用 (a-b)(a+b)=a^2-b^2]
=√2(√6- 1)/10
收錄日期: 2021-04-25 16:54:15
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070425000051KK04755