a)Ta có : vì tam giác ABC cân tại A mà BE,CF lại lần lượt là đường trung tuyến =>BF=CE(1)

Xét tam giác FBC và tam giác EBC,ta có:

góc ABC=góc ACB(gt)

BC cạnh chung

BF=CE(1)

=>tam giác FBC=tam giác ECB(c.g.c)=>BE=CF(đpcm)

b)Áp dụng t/c 3 đường trung tuyến của tam giác cho tam giác CBE và tam giác BFC,ta có:

BG=2/3.BE

CG=2/3.FC

mà BE=FC(câu a)=>BE=FC=>tam giác BGC cân tại G

c)

hình thì bạn nhìn của Nguyễn Thị Thảo nha]

Áp dụng bất đẳng thức cho tam giác BMC,ta có:

MB+MC<BC(điều phải chứng minh)

Tìm x trong hình vẽ sau (làm tròn đến chữ số thập phân thứ hai).

A. x ≈  8,81

B. x  ≈  8,82 

C. x ≈  8,83

D. x  ≈  8,80

Choose the letter A, B, C or D to answer these following questions

Marriage is one of three most important event in one’s life in Vietnam. Wedding custom in Vietnam is quite complicated. Before an official wedding of a couple, a ceremony of engagement must be held first. In accordance with Vietnamese tradition, engagement ceremony is an official occasion for families of fiancé and fiancée to mark their relationship and to arrange the wedding. Each family need to prepare a representative who is a family member having a happy life and high-ranking position in the family. In the day of engagement, the representatives of two families will have some announcement about the wedding and exchange gifts. The time of wedding is chosen suitably based on lunar calendar. Gifts which are put in trays are prepared by the family of fiancé a few days before the engagement ceremony. The number of trays must be an odd number (5, 7, 9, etc.) which is suitable to the condition of the fiancé’s family. In Vietnamese habits, odd numbers are thought to bring luck to the couple. In the trays, there are betel leaves, areca nut fruits, wine, tea, husband-wife and sticky rice. These trays are covered by papers or cloths in red.

Question: How is wedding custom in Vietnam?

A. It’s diverse.

B. It’s cultural

C. It’s complicated.

D. It’s unique.

                Số a là :

                   ( 86 + 10 ) : 2 = 48

                                        Đáp số : a = 48