It is given that sin(A+B) = m sin A, where 0度≤A≤360度; and 180度≤B≤270度;
a) Express tanA in terms of m and B.
b) If m= -7/13 and cos B = -5/13 , find A. (Give your answer correct to 3 significant figures.)
F.4 A.maths 問題
2010-04-04 5:58 am
回答 (2)
2010-04-04 6:16 am
✔ 最佳答案
sin(A+B) = m sin AsinA cosB + cosA sinB = m sinA
sinA (m - cosB) = cosA sinB
tanA = sinB / (m - cosB)
m= -7/13 and cos B = -5/13
(cos B)^2 = 25/169
(sin B)^2 = 1 - (cos B)^2 = 144/169
sinB = -12/13 because 180度≤B≤270度
tanA = (-12/13) / (-7/13 + 5/13 ) = 6
A = 80.5 or A = 261
2010-04-03 22:19:41 補充：
樓上錯左, sinB 變左 sinA
收錄日期: 2021-04-23 20:42:24
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https://hk.answers.yahoo.com/question/index?qid=20100403000051KK01637