這２條數，我想了很多時間，請你幫手唸一唸～～
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數學問題（因唔明）
2008-08-18 9:56 pm
回答 (2)
2008-08-18 10:12 pm
✔ 最佳答案
a. sin(3x+25)=cos(35-x)sin(3x+25)=sin[90-(35-x)]
sin(3x+25)=sin(55+x)
3x+25=55+x
2x=30
x=15
2008-08-18 14:25:06 補充：
b. 請看連結
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2008-08-18 10:15 pm
Q1.
sin(3x + 25) = cos(35 - x) = sin[90 - (35 -x)] = sin(55 + x). Therefore,
3x + 25 = 55 + x
2x = 55 - 25 = 30
x = 15.
Q2.
sqrt3sin^2(45) - sin(90 - x) = 0
sqrt3(1/sqrt2)^2 = sin (90 -x)
sqrt3/2 = sin(90 - x)
cos 30 = sin(90 -x) = cos x
x = 30.
sin(3x + 25) = cos(35 - x) = sin[90 - (35 -x)] = sin(55 + x). Therefore,
3x + 25 = 55 + x
2x = 55 - 25 = 30
x = 15.
Q2.
sqrt3sin^2(45) - sin(90 - x) = 0
sqrt3(1/sqrt2)^2 = sin (90 -x)
sqrt3/2 = sin(90 - x)
cos 30 = sin(90 -x) = cos x
x = 30.
收錄日期: 2021-04-25 22:40:05
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20080818000051KK01503