The focus of the ellipse x ^ 2 + y ^ 2 = 1 is F1, F2, and the point P is the moving point on it. When the angle f1pf2 is an obtuse angle, the abscissa of point P is ∩_ ∩)

The focus of the ellipse x ^ 2 + y ^ 2 = 1 is F1, F2, and the point P is the moving point on it. When the angle f1pf2 is an obtuse angle, the abscissa of point P is ∩_ ∩)

Ellipse X & # 178; + Y & # 178; = 1? Is this an ellipse?
method:
The maximum value of the angle ∠ f1pf2 between the point P on the ellipse X & # 178 / / A & # 178; + Y & # 178 / / B & # 178; = 1 (a > b > 0) and the focus F1 and F2 is obtained when the point P is at the end of the minor axis. To make ∠ f1pf2 an obtuse angle, the obtuse angle can be obtained as long as the point P is at the end of the minor axis

The focus of the ellipse x 2 / 9 + y 2 / 4 = 1 is F 1, F 2, and point P is its upper moving point. When the angle f 1pf 2 is an obtuse angle, the abscissa range of point P is calculated
The elliptic equation is x squared by 9 + y squared by 4 = 1

P is located inside the circle with diameter F1F2
The circle with the diameter of F1F2 is x ^ 2 + y ^ 2 = C ^ 2 = 5
The simultaneous solution with ellipse is: x = plus or minus 3 / root sign 5
So: (- 3 / radical 5,3 / radical 5)