设焦距为 ce=根号2/2则a:b:c=√2:1:1即a=√2b=√2cx=c或-c时,y^2=b^2(1-c^2/a^2)=(b/a)^2(a^2-c^2)=b^4/a^2 |MN|=2|y|=2b^2/a=√22b^2/a=√22b^2=√2a=2bb=1 a=√2所以椭圆方程为x^2/2+y^2=1...