D
duong121234


cho hinh lang chu ABCA'B'C'
3 diemI,J,P
CI=1/3CA
J la` trong tam A'B'C'
B'P=1/2PA
tren dau may cai do deu co vet to
C/m IJP//BCC'B'
3 diemI,J,P
CI=1/3CA
J la` trong tam A'B'C'
B'P=1/2PA
tren dau may cai do deu co vet to
C/m IJP//BCC'B'