=34÷2,
=17(厘米);
答:一条腰长是17厘米.
按要求填空。
无边落木萧萧下,____。(杜甫《登高》)
根据语境和所给首字母完成单词。
Are you busy a____ school? Can you s____ English? Then we n____ you to help w____ sports f____ English-s____ students. It is r____ and easy! Please c____ to the Students' sports c____. C____ Mrs Miller at 6753846.
设椭圆的两个焦点分别为F1,F2,过F2作椭圆长轴的垂线交椭圆于点P,若△F1PF2为等腰直角三角形,则椭圆的离心率是( )