2題F3數(三角形) !!!急!!! 20分!!!

1) Let the third side be x , then
3 + x > 7 , => x > 4
7 + x > 3 , => x > - 4
7 + 3 > x , => x < 10
From the above result : 4 < x < 10
the smallest value of x is 5
So the smallest value of the perimeter = 5 + 3 + 7 = 15cm

2)
From D , draw a line meet AC at G , then by the given that AE=ED,
we have AF = FG
by the given that BD = DC ,
we have FG = GC,
So AF = FG = GC,

FC/AF = (FG+GC)/AF = (AF+AF)/AF = 2



2009-03-29 16:18:54 補充：
The sentence :(From D , draw a line meet AC at G ) is missing something:

Changing to (From D , draw a line 『// BF』 meet AC at G .)