求解y=2.41是怎麼算出來的?

👨🏻‍🏫 學術台數學

[匿名]

2015-09-08 6:38 am

更新1:

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更新2:

已附圖

回答 (2)

Lopez

2015-09-08 8:06 am

✔ 最佳答案

√ [ (3.2y)^2 + y^2 + (-12)^2 ] = 3.2y*3000/1600 = 9600y/1600 = 6y
(3.2y)^2 + y^2 + 144 = 36y^2
( 36 - 3.2^2 - 1 ) y^2 = 144
24.76 y^2 = 144
y^2 = 14400 / 2476 = 120^2 / ( 2^2 * 619 ) = 60^2 / 619
y = 60 / √ 619 ≒ 2.4116 ... Ans

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pui

2015-11-22 1:16 am

1600=3.2y*3000/[(3.2y)^2+y^2+(-12)^2]^0.5
6y=(11.24y^2+144)^0.5
36y^2=11.24y^2+144
24.76y^2=144
y=2.41

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