高中數學題
回答 (2)
2012-05-19 1:54 am
✔ 最佳答案
(√3)/cos290° + 1/sin250°= (√3)/cos(360°-70°) + 1/sin(180°+70°)
= (√3)/cos70° + 1/sin70°
= [(√3)sin70° + cos70°]/(sin70°cos70°)
= 4[(√3/2)sin70° + (1/2)cos70°]/(2sin70°cos70°)
= 4[sin70°cos30° + cos70°sin30°]/sin140°
= 4sin(70°-30°)/sin(180°-40°)
= 4sin40°/sin40°
= 4
參考: 賣女孩的火柴
2012-05-19 1:13 am
收錄日期: 2021-04-13 18:42:06
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20120518000015KK05038