Cho tam giác ABC có góc B = 60 độ, AB=7cm,BC=15cm Trên canh BC lấy D sao cho BAD=60 độ.Gọi H là trung điểm của BD a) Tính độ dài HD b)Tính độ dài AC c) Tam giác ABC có phải tam giác vuông không ? Vì sao ?

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Joining two sentences, using the words in brackets. 1. We must conserve water. Otherwise we will face serious water shortages. (IF) ____________________________________________________________________ 2. The weather was awful. We didn’t enjoy our camping holiday. (BECAUSE OF) ____________________________________________________________________ 3. Plastic bags are non-biodegradable. They will remain in the environment for many years. (SINCE) ____________________________________________________________________ 4. Paul doesn’t think about the planet. He wastes so much water. (IF) ____________________________________________________________________ 5. Water pollution happens. Many aquatic animals such as fish can die. (LEAD) ____________________________________________________________________ 6. The climate is changing. The earth is getting warmer. (BECAUSE) ____________________________________________________________________ 7. We should stop cutting down so many trees. We endanger our oxygen supply. (UNLESS) ____________________________________________________________________ 8. People begin to recycle. They generate much less trash. (WHEN) ____________________________________________________________________ 9. We are damaging the ozone layer. The ozone layer is necessary for human existence. (EVEN THOUGH) ____________________________________________________________________ 10. Sue is suffering from skin cancer. She was exposed to radiation when she was young. (SO) ____________________________________________________________________