题目

阅读理解 The report came to the British on May 21,1941. The German battleship Bismarck, the most powerful warship in the world, was moving out into the Atlantic Ocean. Her task: to destroy the ships carrying supplies from the United States to war-torn England. The British had feared such a task. No warship they had could match the Bismarck in speed or in firepower. The Bismarck had eight 15-inch guns and 81 smaller guns. She could move at 30 nautical miles(海里) an hour, she was believed to be unsinkable. However, the British had to sink her. They sent out a task force headed by their be已知F1、F2是椭圆C：(a＞b＞0)的左、右焦点，c为半焦距，相邻两顶点的距离为，椭圆的离心率为. (Ⅰ)求椭圆的方程； (Ⅱ)直线与椭圆相交于、两点（、不是椭圆的顶点），以 为直径的圆过椭圆C与轴的正半轴的交点，求的值； (Ⅲ)过F2的直线交椭圆C于M、N，求△MF1N面积的最大值.