看圖題! only5題* easy!!

1.a. In triangle ABC and triangle ADE,
　angle CAB = angle EAD (common angle)
　angle ACB = angle AED (corr. angles, BC // DE)
　[angle ABC = angle ADE (corr. angles, BC // DE) ] --- can be omitted
　So triangle ABC ~ triangle ADE (AAA or equiangular)
b. triangle ABC ~ triangle ADE (proved in (a))
　BC/DE = AB/AD (corr. sides, similar triangles)
　x/8 = 5/(5+3) ==> x=5
and AC/AE = AB/AD (corr. sides, similar triangles)
　10/(10+2y) = 5/(5+3)
　80=50 + 10y ==> y=3

2.In triangle ABD and triangle ACD,
　AB = AC (given)
　angle BAD = angle CAD (given)
　AD = AD (common side)
　So triangle ABD ~= triangle ACD. (SAS)

3.Area of the triangle = (12 x 12 x sin 60 / 2) cm^2
　　　　　　　　　 = 72sin 60 cm^2
　Area of each sector = (6 x 6 x Pi x 60/360) cm^2
　　　　　　　　　　=6 Pi cm^2
　So area of "white" region = (72 sin 60 - 3 x 6 Pi ) cm^2
　　　　　　　　　　　　 = 5.81 cm^2 (to 3 sig. fig.)

4.Consider the volume of the water.
　　5 x 5 x Pi x h = 150 Pi
　　　　　　25h = 150
　　　　　　　h = 6
Surface area of the water in contact with the bottle = (10 x Pi x 6 + 5 x 5 x Pi) cm^2
　　　　　　　　　　　　　　　　　　　　　　 = 85 Pi cm^2

5.Volume of this metal tube= (4.5 x 4.5 x Pi x 2 - 3 x 3 x Pi x 2) cm^3
　　　　　　　　　　　　= 70.7 cm^3 (to 3 sig. fig.)

2007-07-12 15:55:09 補充：
Sorry... Q5It should be : (2.25 x 2.25 x Pi x 2 - 1.5 x 1.5 x Pi x 2) cm^3　　　　　　= 17.7 cm^3 (to 3 sig. fig.)

2007-07-12 15:55:10 補充：
Sorry... Q5It should be : (2.25 x 2.25 x Pi x 2 - 1.5 x 1.5 x Pi x 2) cm^3　　　　　　= 17.7 cm^3 (to 3 sig. fig.)

1A)
cab <大家都有的角
acb abc<<同位角*要講有對平行line
因為AAA
so 佢地相似
1B)
因為相似,so d邊成比例
5+3:5=10:10+2y
y=3
8:x=5+3:5
x=5
............有排打= =........之後你都係自己+ oil啦................