Bóng của một cột cờ trên mặt đất dài 4m. a) Biết cột cờ cao 7m, tính góc mà tia sáng mặt trời tạo với mặt đất. b) Giả sử tia nắng tạo với cột cờ một góc 38 độ. Tính khoảng cách từ đỉnh cột cờ đến bóng của nó trên mặt đất.

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