VẼ MH  BC, BK  AC. SAMNB = 3SMNC SABC = 4SMNCS ACTA CÓ

10.

Vẽ MH  BC, BK  AC.

S

AMNB

= 3S

MNC

 S

ABC

= 4S

MNC

S AC

Ta có: 3

ABC

2

S  MC 

BMC

S BC S

6 9

BMC ABC

S  NC  NC  S  NC

MNC MNC

Mà S

ABC

= 4S

CMN

 NC = 2,25