Maths MC _ 4
2009-07-24 6:27 am
回答 (1)
2009-07-24 6:39 am
✔ 最佳答案
1)Since 5^2 = 3^2 + 4^2
So △ABC is an right angle △, ㄥB = 90
tan A = CB/AB = 4/3
cos C = CB / AC = 4/5
tan A : cos C = 4/3 : 4/5 = 5 : 3
(D)
2)
cos^2 A + sin^2 B
= cos^2 A + sin^2 (90 - A)
= cos^2 A + cos^2 A
= 2cos^2 A
(C)
收錄日期: 2021-04-21 22:02:22
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https://hk.answers.yahoo.com/question/index?qid=20090723000051KK02200