Cho tam giác \(ABC\) có bán kính đường tròn ngoại tiếp bằng \(2\). Nếu \(2\text{sin}A+\text{sin}C=1\) thì tổng \(AB+2BC\) bằng
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Câu 12
Theo định lí sin trong tam giác ta có
\(\text{sin}A=\frac{BC}{4}\); \(\text{sin}C=\frac{AB}{4}\).
\(\Rightarrow 2\text{sin}A+\text{sin}C=1\)
\(\Leftrightarrow 2\frac{BC}{4}+\frac{AB}{4}=1\)
\(\Leftrightarrow 2BC+AB=4.\)
Bộ Đề Kiểm Tra Giữa Học Kì I - Toán 10 - Chân Trời Sáng Tạo là tài liệu cung cấp bài tập chuyên sâu, tập trung vào các kiến thức cốt lõi như hàm số bậc nhất, bậc hai, phương trình, bất phương trình, và căn bậc hai. Đề thi được thiết kế với các câu hỏi đa dạng, từ việc nhận diện đặc điểm hàm số đến giải phương trình phức tạp, giúp học sinh rèn luyện kỹ năng phân tích và tư duy giải toán logic. Đây là tài liệu cần thiết để học sinh làm quen với các dạng bài toán nâng cao, tối ưu hóa kỹ năng tính toán và lập luận, tạo nền tảng vững chắc cho các kỳ thi tiếp theo.
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(Nguồn: nongnghiep.vn)
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Chọn một từ mà nghĩa của nó KHÔNG cùng nhóm với các từ còn lại.
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4. So, it is clear you should not use your phone before you go to sleep. Why not leave it in another room? Nothing on social media is so important that it cannot wait a few hours! You should rediscover paper books and enjoy feeling tired and sleepy before bedtime rather than wondering why your best friend has not liked your photo! How will you wake up? You do not have to use the alarm on your phone. Go and buy yourself an old-fashioned alarm clock! The negative effects that screen time is having on sleep have been in the news a lot recently, so manufacturers of smartphones and tablets have added a feature to the mobile devices that can help reduce these. Most new phones have a night-time setting that changes the colour of the screen so that it gives out less blue light. If you really cannot avoid going onto social media at bedtime, think about turning on this setting on your phone.
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1990’s fashion was far more subdued than the garish, wild styles of the 1980s. Bands like Nirvana influenced the grunge look, which featured rock-concert tee shirts under plaid flannel shirts, jeans and long, greasy hair. Overalls were worn by both sexes, either with one or both shoulder straps unhooked. The punk style of the 1870s and 1980s evolved into the goth fashion trend, which featured black clothing, black boots and studded bracelets in the style of bands like Nine Inch Nails and Marilyn Manson.
The phrase “gave rise to” in paragraph 1 mostly means ______.