đề tuyển sinh 2008-2009

R

riverflowsinyou1

Ta có : tam duog tron noi tiep tam giac la giao cua 3 duog phan giac >>> AD la phan giac cua goc A >>> goc BAD=goc CAD >>> cug BD=cung CD>>>BD=CD ( * )
xet tam giac ODC ta co:
goc DOC= goc OAC+ goc OCA ( vi DOC la goc ngoai cua tam giac AOC)
goc OCD=goc OCB+ goc BCD
ma goc OCB=goc OCA ( CO la phan giac cua goc C)
goc OAC=goc BCD ( cung BD=cung CD)
>>> goc DOC=goc OCD
vay tam giac OCD can tai D
>>> OD=CD (**)
tu * va ** >>> OD=CD=BD
Trích : yahoo
 
You must log in or register to reply here.
Top Bottom