Question

已知双曲线X^2/9-Y^2/16=1的左右焦点分别为F1,F2 P为C右支上一点,且|PF2|=|F1F2|则三角形P

Answer 1

PF2=ex.-a =2c =10 pf1=ex.+a

ex.=2c+a pf1=2c+2a=16

pf1=16 pf2=10 2c=10

cos=100+256-256/2*10*16=5/16

sin^2=1-cos^2 s=sinpf2*2c/2 可求s