三角比問題
回答 (5)
2007-04-29 10:31 pm
✔ 最佳答案
tan10°tan80°-sin60°cos3 0° =cot(90°-10°)tan80°-sin60°sin(90°-30°)
=cot80°tan80°-sin^2 60°
=1-(3/4)
=1/4
2007-05-01 2:33 am
tan10tan80 - sin60cos30
= cot80 tan80 - [ (root 3) / 2 ] [ (root3) / 2]
= (1/ tan80)(tan80) - 3/ 4
= 1 - 3/4
= 1/4
By law,
tan @ = cot ( 90 - @ )
tan @ = 1/ cot @
= cot80 tan80 - [ (root 3) / 2 ] [ (root3) / 2]
= (1/ tan80)(tan80) - 3/ 4
= 1 - 3/4
= 1/4
By law,
tan @ = cot ( 90 - @ )
tan @ = 1/ cot @
參考: Keith ^^
收錄日期: 2021-04-13 00:25:48
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070429000051KK02353