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1)
In the figure, the length of each side of square ABCD is 7cm. P is a point inside the square. If PA=PB=AB, find DP.
圖片參考：http://i524.photobucket.com/albums/cc324/orzxdxp/fig.jpg
2)
In the figure, when a metal sphere is completely submerged in a cylindrical vessel of base diameter 64cm, the water level rises by 2/3 cm. Find the radius of the sphere.
圖片參考：http://i524.photobucket.com/albums/cc324/orzxdxp/fig-1.jpg
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maths唔識--------11點前要~~急急急= =''
2009-03-03 6:35 am
回答 (2)
2009-03-03 7:51 am
✔ 最佳答案
1)PA = PB = AB (given)
ΔAPB is equilateral.
Hence, PAB = 60o (int. s of equil. Δ)
DAB = 90o (int. of sq.)
DAP
= DAB - PAB
= 90o - 60o
= 30o
AB = AD = BC = 7 cm (sides of sq.)
Hence, PA = PB = AB = 7 cm
Consider ΔDAP. By sine law,
DP2 = AD2 + AP2 - 2AD•AP•cosDAP
DP2 = [(7)2 + (7)2 - 2(7)(7)cos30o] cm2
DP = 3.623 cm
2.
Let the radius of the sphere be r cm.
Volume of the sphere = Volume of water rises
(4/3)πr3 = π(64/2)2(2/3)
(4/3)r3 = 2048/3
r3 = 512
r = 8
The radius of the sphere is 8 cm.
=
2009-03-03 7:48 am
1. PD^2 =7^2+7^2 -2X7Xcos30度
PD^2 =自己算下啦~
PD^2 =自己算下啦~
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