A(x1,y1) B(x2,y2)
PF1:y=-2x-2
x²/2+y²=1
联立方程得9y²+4y-4=0
所以得y1+y2=-4/9 y1y2=-4/9
所以 S△=[2c(|y1|+|y2|)]/2
=√{(y1)²+(y2)²+2|y1||y2|}
=√{(y1)²+(y2)²-2*y1*y2} ----------------------------这步是因为|y1||y2|>0 ,y1y2
A(x1,y1) B(x2,y2)
PF1:y=-2x-2
x²/2+y²=1
联立方程得9y²+4y-4=0
所以得y1+y2=-4/9 y1y2=-4/9
所以 S△=[2c(|y1|+|y2|)]/2
=√{(y1)²+(y2)²+2|y1||y2|}
=√{(y1)²+(y2)²-2*y1*y2} ----------------------------这步是因为|y1||y2|>0 ,y1y2