form2 maths triangle 工作紙

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因為打出黎太煩 所以scan左佢算
希望幫度你

2008-05-15 22:51:30 補充：
4c個度做錯左
應該係 FC/BC = 2/(2+1) = 2/3
FG/BD = 2/BD = 2/3 BD = 6

3)a)∠BNM=∠AND(vert. opp. ∠s)
∠BMN=∠ADN(alt. ∠s,AD//BC)
∠NBM=∠DAN(alt. ∠s,AD//BC)
∴ΔAND~ΔBNM(AAA)
b)BC=AD(opp. sides of // gram)
∴AD=2BM
2BN=ND
BD=BN+ND
BD=3BN
BN=1/3BD

4)a)∠EBF=∠ABC(common ∠)
∠EFB=∠ACB(corr. ∠s,EF//AC)
∠FEB=∠CAB(corr. ∠s,EF//AC)
∴ΔBEF~ΔBAC
b)∠GCF=∠DCB(common ∠)
∠CGF=∠CDB(corr. ∠s,FG//BD)
∠CFG=∠CBD(corr. ∠s,FG//BD)
∴ΔCGF~ΔCDB(AAA)
c)∵AC:EF=3:1(corr. sides of congruent triangles)
∴BC:BF=3:1(corr. sides of congruent triangles)
BD:FG=3:1(corr. sides of congruent triangles)
BD:2=3:1
BD=6

5)a)∠ADC=∠GDE(vert. opp. ∠s)
∵ΔABC~GFE(AAA)
∠BAC + ∠CBA = ∠FGE + ∠EFG(corr. ∠s of congruent Δs)
∠ACD=∠GED(ext. ∠s of Δ)
∴∠CAD=∠EGD
ΔACD~ΔGED(AAA)
b)∵∠ADC=∠GDE(proved)
∠BAC = ∠FGE(proved)
∠CBA = ∠EFG(proved)
∴ΔABD~ΔGFD(AAA)