1 x^2/9-y^2/16=1
a=4,b=3 c^2=a^2+b^2=25,c=5
|PF1-PF2|=2a=8
2|PF1PF2|cosF1PF2=F1P^2+F2P^2-F1F2^2
2|PF1PF2|(cosF1PF2-1)=(F1P-F2P)^2-F1F2^2
2*32*(cosf1pf2-1)=8^2-100
cosf1pf2-1=-1/2
cosf1pf2=1/2
角f1pf2=60
2
e=c/a=√2 c^2/a^2=2 b^2=a^2
x^2/a^2-y^2/a^2=1
16-10=a^2
a^2=6,c^2=12,x^2-y^2=6
F1(-2√3,0) F2(2√3,0)
m^2=3^2-6=3
m=√3
MF1(3-2√3,√3) MF2(3+2√3,√3)
MF1MF2=(3-2√3)(3+2√3)+√3*√3=0
m=-√3
MF1(3-2√3,-√3) MF2(3+2√3,-√3)
MF1*MF2=(3-2√3)(3+2√3)+(-√3)*(-√3)=0