Given that the distance from a point P on the hyperbola X & # 178 / 36-y & # 178 / 64 = 1 to a focus of the hyperbola is equal to 9, find the perimeter of △ pf1f2

Given that the distance from a point P on the hyperbola X & # 178 / 36-y & # 178 / 64 = 1 to a focus of the hyperbola is equal to 9, find the perimeter of △ pf1f2

A = 6, B = 8, then C = radical (36 + 64) = 10,
According to the definition of hyperbola, the distance difference between two focal points of a point is 2A,
The distance from P to another focus is: 9 + 2 * 6 = 21; F1F2 = 2C = 20; F1F2 = 2C = 20;
So the perimeter is C = 9 + 21 + 20 = 50