Hyperbola
x<√a2+b2
0°<∠PF2F1<30°
x→a
∠PF2F1 → 0°
x=√a2+b2
∠PF2F1 = 90°
√a2+b2 <x
30°<∠PF2F1<90°
x→∞
∠PF2F1 → 90°
x<√a2+b2
90°<∠PF1X<180°
x→a
∠PF1X →180°
x=√a2+b2
∠PF1X = 90°
√a2+b2 <x
0°<∠PF1X<90°
x→∞
∠PF1X→ 0°
T.theodor 2022.8.26