= 4
e² = c²/a² = (a² - b²)/a² = (a² - 16)/a² = 9/25
a² = 25, a = 5
按椭圆的定义:
△ABF2的周长 = AB + AF2 + BF2 = AF1 + F1B + AF2 + BF2 = AF1 + AF2 + F1B + BF2 = 2a + 2a = 4a = 20
= 4
e² = c²/a² = (a² - b²)/a² = (a² - 16)/a² = 9/25
a² = 25, a = 5
按椭圆的定义:
△ABF2的周长 = AB + AF2 + BF2 = AF1 + F1B + AF2 + BF2 = AF1 + AF2 + F1B + BF2 = 2a + 2a = 4a = 20