∴a=3 b=4 c=5 F 1(-5，0).F2(5，0)

P(x 1, y 1) y 1 is the distance from point p to the x axis.

∵PF 1⊥PF2

∴│pf 1│^+│pf2│^=│f 1f2│^=4c^= 100

│PF 1│-│PF2│=2a=6

∴(│pf 1│-│pf2│)^+2│pf 1││pf2│= 100

( 1/2)│pf 1│PF2 │= 16

Triangle PF 1F2 region

s =( 1/2)×│f 1 F2│×│y 1 │=( 1/2)│pf 1│PF2 │= 16

∴y 1= 16/5