.SIN 60 S AB ACABC2VÌ SANCSANB SABC NÊN 1 1 1. .SIN 60 . .SIN...
1 . .sin 60 S AB AC
ABC
2Vì SANC
SANB
SABC
nên 1 1 1. .sin 60 . .sin 60 . .sin 602AN AC 2AN AB 2AB AC Do đó AN ACABC
2Vì SANC
SANB
SABC
nên 1 1 1. .sin 60 . .sin 60 . .sin 602AN AC 2AN AB 2AB AC Do đó AN AC