设椭圆方程为x^2/a^2+y^2/b^2=1,或者x^2/b^2+y^2/a^2=1
BF1=BF2=a,F1F2=2c
BF1+BF2+F1F2=4+2√2=2a+2c,a+c=2+√2
F1BF2=2π/3,F1BO=π/3,b=1/2a,c=√3/2a
√3/2a+a=2+√2,a=2(4+2√2-2√3-√6)
b=1/2a=4+2√2-2√3-√6
将a,b代入即可