數學知識交流 － 求值
回答 (1)
2012-05-27 11:47 pm
✔ 最佳答案
sin²x + cos²x = 9 sin²y + (cos²y) / 44 = 36 sin²y + cos²y
3 = 35 sin²y
sin²y = 3/35
sin²y + cos²y = (sin²x)/9 + 4cos²x
9 = sin²x + 36cos²x
8 = 35cos²x
cos²x = 8/35
∴ sin2x / sin2y + cos2x/cos2y
= 2sinx cosx / (2siny cosy) + (2cos²x - 1) / (1 - 2sin²y )
= 3/2 + (2*8/35 - 1) / (1 - 2*3/35)
= 49/58
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原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20120527000051KK00305