Cho hình vẽ bên:

Chứng tỏ Ot và Ot’ là hai tia đối nhau.

Cho tam giác ABC vuông tại A có B ^ =   55 ° . Trên nửa mặt phẳng bờ AC không chứa B, vẽ tia Cx vuông góc với AC. Trên tia Cx lấy điểm D sao cho CD = AB.

a) Tính số đo  A C B ^

b) Chứng minh ∆ A B C   =   ∆ C D A  và AD//BC.

c) Kẻ A H ⊥   B C   ( H ∈   B C ) và C K ⊥   A D   ( K   ∈   A D ) . Chứng minh BH = DK.

d) Gọi I là trung điểm của AC. Chứng minh ba điểm H, I, K thẳng hàng và 3 đường thẳng AC, HK, BD cùng gặp nhau ở I.

Cho  x O y ^  tù. Trong góc xOy vẽ các tia  O m ⊥ O x , O n ⊥ O y . Chứng tỏ:

a)    a.  x O n ^ = y O m . ^

b.  x O y ^ và  m O n ^ có chung tia phân giác

Cho tam giác ABC, gọi M là trung điểm cạnh BC. Trên tia đối của tia MA lấy điểm D sao cho MD = MA.

a) Chứng minh AB = CD và AB //CD.

b) Chứng minh BD// AC.

c) Chứng minh  ∆ A B C   = ∆   D C B .

d) Trên các đoạn thẳng AB,CD lần lượt lấy các điểm E, F sao cho AE = DF. Chứng minh, ba điểm E, M, F thẳng hàng.

Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best combines each of sentences in the following questions.

I didn't know that you were at home. I didn't drop in.

A. Not knowing that you were at home, but I still dropped in,

B. I didn't know you were at home although I didn't drop in.

C. Not knowing that you were at home, I didn't drop in.

D. If I knew that you were at home, I would drop in.

Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that best combines each of sentences in the following questions.

I started training to be an accountant one year ago. I had more months to go and then I had to take exams.

A. By the time I've taken my exam, I will have started training to be an accountant for a year

B. By the time I take my exam, I will have been in training to be an accountant for a year.

C. By the time I took my exam, I had been trained to be an accountant for a year.

D. By the time I've taken my exam, I will be training for a year.

Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that is closest in meaning to each of the following questions.

"Shall I help you do the dishes, Carlo?" said Robert.

A. Robert suggested helping Carlo with the dishes.

B. Robert suggested to help Carlo do the dishes.

C. Robert offered Carlo to help do the dishes.

D. Robert offered to help Carlo do the dishes.

Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that is closest in meaning to each of the following questions.

The accident happened as a result of the driver's not paying attention to the road.

A. If the driver would have paid attention to the road, the accident hadn't happened.

B. Had the driver been paid attention to the road, the accident wouldn't have happened.

C. If the driver had been paying attention to the road, the accident wouldn't have happened.

D. Had the accident not happened, the driver would not have had to pay attention to the road.

Cho  x O y ^ = 140 0 . Trong góc xOy vẽ các tia  O m ⊥ O x , O n ⊥ O y

a. Tính  m O n ^

b. So sánh:  x O n ^ ,   y O m . ^