It is known that the two focal points of hyperbola x ^ 2 / 9-y ^ 2 / 16 = 1 are F1 and F2 respectively, the point P is on the hyperbola, and | Pf1 | x | PF2 | = 32, so the size of angle f1pf2 is calculated

It is known that the two focal points of hyperbola x ^ 2 / 9-y ^ 2 / 16 = 1 are F1 and F2 respectively, the point P is on the hyperbola, and | Pf1 | x | PF2 | = 32, so the size of angle f1pf2 is calculated

There is a hyperbolic definition | Pf1 | - | PF2 | = 2A = 6 C ^ 2 = a ^ 2 + B ^ 2 = 25 C = 5 | Pf1 | ^ 2 + | PF2 | ^ 2 = [(| Pf1 | - | PF2 |) ^ 2 + 2 | Pf1 | PF2 | = 6 ^ 2 + 64 = 100 | F1F2 | ^ 2 = (2C) ^ 2 = 100 | Pf1 | ^ 2 + | PF2 | ^ 2 = | F1F2 | ^ 2, so the angle f1pf2 = 90 degree