f3 mth questions!!!急~

Is AF//BH given?
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(if yes)
1.because AF//BH and FH//GH (given)
therefore AFBH is a parallogram( opp. side //)

Therefore AF=BH (opp. side of //gram)
=6 cm

2. Because BE=EH and AB//DE (given)
therefore AD=DG (intercept theorem)
because AG=AF (given)
therefore AD=(1/2)AF
=3 cm


3.because AFBH is a parallogram (proved)
therefore AB=FH (opp side of //gram)
therefore FG+GH=AB
FG=7-5=2 cm

4. because AC=CF and AD=DG (proved)
therefore CD=(1/2)FG
=1 cm
because AC//BE and AC=BE (proved)
therefore ACBE is a parallogram (2 sides eq and //)
therefore CE=AB (opp side of //gram)
therefore CD+DE=AB
DE=7-1=6 cm












2011-04-04 17:04:25 補充：
To prove AF//BH:

because AF=AG ( given)
therefore





2011-04-04 17:11:57 補充：
To prove AF//BH:

because AF=AG ( given)
therefore





2011-04-04 17:12:13 補充：
To prove AF//BH:
because AF=AG ( given)
therefore

2011-04-04 17:13:14 補充：
therefore





2011-04-04 17:14:21 補充：
therefore AFG=AGF(base





2011-04-04 17:15:32 補充：
To prove AF//BH:
because AF=AG ( given)
therefore AFG=AGF(base angles isos △)
AGH=BHG (given)
AGH+AGF=180 (adj < on st line)
therefore BHG+AFG=180
therefore AF//BH (int. angles, supp)

i cant type angle in short from because of the dumb system-.-

First, notice that <AGH =<BHF, <AGF = 180 - <AGH and since <AFG =<AGF => <AFG + <BHF = 180 => AF//BH. So, ABHF is a parallelogram.

(1) AF = 6 cm by the properties of parallelogram.

(2) AD = (1/2)AG = (1/2)AF = 3 cm

(3) FG = 7 - 5 = 2 cm

(4)DE = 7 - CD = 7 - 1 = 6 cm

2011-04-04 22:45:38 補充：
同旁內角和等於180度