设椭圆<img src="https://storage.tutusouti.com/pzst/question_bank/res/7e/a6/7ea6dfaaa324dd9d114fafe726961f1f4362406d.jpg?x-oss-process=image/sharpen,200"/>：<img src="https://storage.tutusouti.com/pzst/question_bank/res/97/ba/97babfda99c3633f2bbd8c016461971208da4427.jpg?x-oss-process=image/sharpen,200"/>的周长为<img src="https://storage.tutusouti.com/pzst/question_bank/res/36/9f/369fb4af2538b6babaf6d00eafe2014909b3afef.jpg?x-oss-process=image/sharpen,200"/>，则<img src="https://storage.tutusouti.com/pzst/question_bank/res/22/f6/22f6201bf09d1063fd664721f097243cd7aff9b7.jpg?x-oss-process=image/sharpen,200"/>（）