[form2]Pyth.theorem,求教(20分)

(3y)^2+(2y)^2=10^2(Pyth.theorem)
9y^2+4y^2 =100
13y^2 =100
y^2 =100/13
y =sqrt100/13
y =(10sqrt13)/13

2010-06-06 16:20:56 補充：
b=20
a+c=50
a =50-c

20^2+c^2=(50-c)^2(Pth.theorem)
400+c^2 =2500-100c+c^2
100c =2500-400
100c =2100
c =21

a+c=50
a+21=50
a =29

2010-06-06 16:32:15 補充：
x^2+y^2=7^2(Pyth.theorem)
y^2 =49-x^2
y =sqrt49-x^2

(9-x)^2+(sqrt49-x^2)=5^2(Pyth.theorem)
81-18x+x^2+49-x^2=25
-18x =25-49-81
-18x =-105
x =105/18
x =35/6

BD=9-(35/6)=3.17(cor.to 3 sig.figs.)

2010-06-06 16:34:35 補充：
AB^2+4^2=(3AB)^2(Pyth.theorem)
AB^2+16 =9AB^2
-8AB^2....=-16
AB^2 =2
AB =sqrt2

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