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The second volume of geometry mathematics problems in the first day of junior high school
(2) It is proved that CG=CE is intercepted on CB, which is determined by ∠ECO=∠GCO and OC=OC.

Get: △ CEO △ CGO (SAS),

∴∠EOC=∠GOC,EO=GO,

According to the theorem of triangle interior angle sum, in △ABC,

2∠EBC+2∠FCB+60 = 180,

The solution is ∠ EBC+∠ FCB = 60,

At △DBC, ∠ BDC =180-(∠ EBC+∠ FCB) =180-60 =120.

∴∠FDE=∠BDC= 120,

∵∠BOG+∠GOC= 120,

∵∠ BOG+2∠ GOC = 180,

Solution: ∠ BOG = ∠ GOC = ∠ EOC = 60.

In △BFO and △BGO, ∠FBO=∠GBO, ∠ FOB = ∠ GOB = 60, BO=BO,

∴△BFO≌△BGO,

∴FO=OG,

∴FO=EO.