a. Kẻ \(O H ⊥ A M\); \(O^{'} K ⊥ M B\) suy ra \(O H\) // \(O^{'} K\).

Tứ giác \(H K O O^{'}\) là hình thang, \(M I ⊥ A B\) suy ra \(M I\) // \(O H\) và \(I O\) // \(I O^{'}\)

Suy ra \(M H = M K\). 

Mà \(O H ⊥ A M\) suy ra \(H A = H M = M K = K B\) (đpcm).

b. Ta có \(M E\) là đường trung bình của hình thang \(A B Q P\)

Suy ra \(E P = E Q\).

c. Xét \(\Delta H I K\), có \(I M\) là đường trung tuyến đồng thời là đường cao.

Suy ra \(\Delta H I K\) cân tại \(I\) (đpcm).

a. \(\mid O I - O K \mid < I K < O I + O K\) suy ra \(\left(\right. I \left.\right)\) và \(\left(\right. K \left.\right)\) luôn cắt nhau

b. Do \(O I = N K\); \(O K = I M\) suy ra \(O M = O N\),

Mà \(O M C N\) là hình chữ nhật nên \(O M C N\) là hình vuông.

c. Gọi \(L\) là giao điểm của \(K B\) và \(M C\); \(P\) là giao điểm của \(I B\) và \(N C\)

Suy ra \(O B K I\) là hình chữ nhật và \(B L M I\) là hình vuông nên \(\Delta B L C = \Delta K I O\)

Suy ra \(\hat{L B C} = \hat{O K I} = \hat{B I K}\)

Mà \(\hat{B I K} + \hat{I B A} = 9 0^{\circ}\) suy ra \(\hat{L B C} + \hat{I B A} = 9 0^{\circ}\)

Do đó, \(\hat{L B C} + \hat{L B I} + \hat{I B A} = 18 0^{\circ}\).

d. Có \(O M C N\) là hình vuông cạnh \(a\) cố định nên \(C\) cố định và \(A B\) luôn đi qua \(C\).

a) \(\Delta B C D\) có \(O O^{'}\) là đường trung bình suy ra \(O O^{'}\) // \(C D\) (1)

\(\Delta A B C\) có \(O I\) là đường trung bình suy ra \(O O^{'}\) // \(C A\) (2)

Từ (1) và (2) suy ra \(C\), \(A\), \(D\) thẳng hàng.

b) Ta có: \(\Delta O B O^{'}\) vuông tại \(B\) suy ra \(\Delta B C D\) vuông tại \(B\)

Suy ra \(S_{B C D} = \frac{1}{2} . B C . B D = \frac{1}{2} . 8.6 = 24\) (cm\(^{2}\)).

a) Ta có: \(12 - 5 < 13 < 12 + 5\) hay \(R - R^{'} < d < R + R^{'}\) nên hai đường tròn \(\left(\right. O \left.\right)\) và \(\left(\right. O^{'} \left.\right)\) cắt nhau tại hai điểm phân biệt

b) \(O A^{2} + O^{'} A^{2} = 1 2^{2} + 5^{2} = 169\);

\(O^{'} O^{2} = 1 3^{2} = 169\)

\(\Delta O A O^{'}\) có: \(O A^{2} + O^{'} A^{2} = O^{'} O^{2}\), theo định lí Pythagore đảo suy ra tam giác \(\Delta O A O^{'}\) vuông tại \(A\).

Có \(O A ⊥ O^{'} A\) do đó \(O A\) là tiếp tuyến của đường tròn \(\left(\right. O^{'} \left.\right)\) và \(O^{'} A\) là tiếp tuyến của đường tròn \(\left(\right. O \left.\right)\).

\(O^{'} O\) là đường trung trực của đoạn \(A B\).

Gọi \(H\) là giao điểm của \(O^{'} O\) và \(A B\) nên \(A H . O^{'} O = O A . O^{'} A\) suy ra \(A H = \frac{O A . O^{'} A}{O^{'} O} = \frac{12.5}{13} = \frac{60}{13}\) cm.

Vậy \(A B = 2 A H = \frac{120}{13}\) cm.

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What are its advantages?

- What are its disadvantages?

- Will people use it in the future?

Topic 1:

Dear Mai,

I want to share some tips about what to do in a flood. Before a flood, you should prepare clean water, food, flashlights, and important documents. You also need to listen to weather forecasts. During a flood, stay inside or move to higher ground. Do not walk or drive through deep water because it is dangerous. Turn off electricity if water enters the house. After the flood, clean the house carefully and boil water before drinking. You should also check for damage and help neighbors if possible.

I hope you find these tips helpful.

Love,

Lan

Topic 2:

Shopping in a supermarket has both advantages and disadvantages. One advantage is that customers can find many different products in one place. Prices are usually clear, and there are often discounts. Supermarkets are also clean and comfortable. However, there are some disadvantages. Some products may be more expensive than in local markets. Supermarkets can also be crowded on weekends, which makes shopping stressful. In addition, customers may buy unnecessary items because of attractive displays. Overall, supermarkets are convenient, but people should shop carefully and plan their spending.

Topic 3:

Global warming has serious effects on our planet. First, it causes higher temperatures and more extreme weather, such as storms and droughts. Second, it makes ice in the polar regions melt, and this makes sea levels rise. This can lead to floods in coastal areas. Third, many animals lose their natural habitats because of climate change. Farmers may also face problems growing crops due to heat and lack of water. As a result, food prices can increase. If we do not take action, the situation may become worse. Therefore, protecting the environment is very important for our future.

1. Planting trees helps to reduce pollution and provides homes for many animals.

2. The supermarket provides a wide range of products at reasonable prices.

1. It took John an hour to browse for new clothes on Lazada.

2.The flood destroyed many homes, but; however, no one was badly injured.

3. If communities don’t work together, the forest won’t recover quickly.

Shopping in local stores has some great advantages. First, it is good for people who like to see and touch things before buying them. You can try clothes on to make sure they fit right. Also, local stores usually have friendly staff. They can help you find what you need and answer questions. Another good thing is that shopping locally supports your community. The money you spend helps local business owners. Plus, local stores often have unique things that you cannot find in big supermarkets or online. This makes shopping more interesting. So, shopping at local stores can be a really nice experience.