xét tam giác ABC có BN là đường phân giác của góc B nên:

AN/NC = AB/BC ( tính chất đường phân giác trong tam giác )

hay AN/NC = b/a

Áp dụng tính chất tỉ lệ thức ta có

AN/AN+BC = b/b+a

suy ra AN/AC = b/b+a

suy ra AN = b^2/a+b

xét tam giác ABC có CM là đường phân giác góc C nên

AM/BM = AC/BC

hay AM/BM = b/a

Áp dụng tính chất tỉ lệ thức ta có:

AM/AM+BM=b/a+b

hay AM/AB = b/a+b

suy ra AM = b^2/a+b

Vì AM=AN và AB=AC=b suy ra AM/AB = AN/AC

theo định lý thales đảo suy ra MN song song BC

Áp dụng hệ quả Thales ta có:

MN/BC = AN/AC

suy ra MN/a = b/a+b

suy ra MN = a*b/a+b

vì tam giác ABC cân tại A nên AB = AC = 12 cm

xét tam giác ABC có CD là đường phân giác của góc C:

AD/CA = DB/BC

hay AD = CA*DB/BC

hay AD = 12*DB/6

suy ra AD = 2DB (1)

Ta có: DA + DB = AB = 12 cm (2)

từ (1) và (2) suy ra DA + DB = 12 cm

hay 2DB + DB = 12 cm

3DB = 12 cm

suy ra DB = 4 cm

suy ra AD = 2DB = 2*4 = 8

At New Year, my family keeps many special traditions that make the holiday warm and joyful. Before Tet, we clean the house carefully and decorate it with flowers and lights to welcome good luck. On New Year’s Eve, we enjoy a big family dinner, talk happily, and watch fireworks together. In the following days, we visit relatives, give lucky money, and wish everyone health, peace, and success.

At New Year, my family keeps many special traditions that make the holiday warm and joyful. Before Tet, we clean the house carefully and decorate it with flowers and lights to welcome good luck. On New Year’s Eve, we enjoy a big family dinner, talk happily, and watch fireworks together. In the following days, we visit relatives, give lucky money, and wish everyone health, peace, and success.

1. If you don't drink more water, you will get more acne.

2. My sister wants to see the terraced fields; therefore, she is going to Sa Pa.

3. Unless he spend time on his phone, he will complete his work.