Current location - Training Enrollment Network - Mathematics courses - The Second Model of Mathematics in Chongming District
The Second Model of Mathematics in Chongming District
( 1)∵AB=AC,AD= 12AC,AE= 12AB,

∴AD=AE,

In △BAD and △CAE,

AB=AC∠BAD=∠CAEAD=AE,

∴△BAD≌△CAE.

∴∠ABD=∠ACE,

∵DF⊥AC,AD=CD,

∴AF=CF,

∴∠GAD=∠ACE,

∴∠GAD=∠ABD.

∠∠GDA =∠ADB,

∴△GDA∽△ADB.

∴ADDB=DGAD,

∴AD2=DG? BD。

(2)∫ADDB = DGAD,AD=CD,

∴CDDB=DGCD.

∠∠CDG =∠BDC,

∴△DCG∽△DBC.

∴∠DBC=∠DCG.

AB = AC,

∴∠ABC=∠ACB.

∵∠ABD=∠ACE,

∴∠ECB=∠DBC=∠DCG,

∴∠ECB=∠DCG.