好心人Pls. help help幫幫忙牙?
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M2 Trigonometry
2012-05-26 4:03 pm
回答 (3)
2012-05-26 10:46 pm
✔ 最佳答案
(a) perimeter of sector = 10 cm=> 2x+xθ=10
=> θ=(10-2x)/x
(b) A=(1/2) x² θ=(1/2) x² [(10-2x)/x]=5x-x²
(c) A = 5x-x² = (5/2)²-(5/2)²+5x-x² = 25/4 - (5/2 - x)² <= 25/4
=> greatest value of A is 25/4 which occurs when x=5/2
2012-05-27 3:48 pm
希望好心人補充一下 c)
小弟蠢少少, 不明白 5/2 怎來?
小弟蠢少少, 不明白 5/2 怎來?
2012-05-26 7:59 pm
10=xθ+2xθ=(10-2x)/xA=(1/2)x²θ=(x/2) (10-2x)=5x-x²dA/dx=5-2x=0x=5/2A=25/4
2012-05-27 08:06:18 補充：
dA/dx=0
5-2x=0
x=5/2
2012-05-27 08:06:18 補充：
dA/dx=0
5-2x=0
x=5/2
收錄日期: 2021-04-16 15:21:26
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20120526000051KK00069