When a light passenger plane flew off course some time (1) , it crashed (2) the mountains and its pilot was killed. (3) only passengers, a young woman and her two baby daughters were unhurt. It was the (4) of winter. Snow lay thick (5) the ground. The woman knew that the nearest village was miles (6) . When it grew dark, she turned a suitcase (7) a bed and put the children inside it, covering them (8) all the clothes she could find. During the night, (9) got terrible cold. The woman kept as near as she (10) to the children and even tried to get into the case herself, but it was too small. Early the (11) morning, she heard planes passing overhead and wondered how she could (12) a signal. Then she had an idea. She stamped out the letters “SOS” in the snow. Fortunately, a pilot saw the signal and sent a message (13) radio to nearest town. It was not (14) before a helicopter arrived on the scene and (15) the survivors of the plane crash.
Cho tam giác ABC vuông tại A, trung tuyến AM, D là trung điểm của AB.Gọi E là điểm đối xứng với M qua D, F là điểm đối xứng với A qua M.
a) Tứ giác AEMC là hình gì ? Vì sao ?
b) Chứng minh: tứ giác ABFC là hình chữ nhật.
c) Chứng minh: AB ⊥ EM.
d) Biết AB = 3cm, BC = 5cm. Tính diện tứ giác ABFC