===》x^2/9-y^2/16=1,a^2=9,b^2=16,c^2=25,||PF1-PF2|=2a=6,F1F2=2c=10,
CosF1PF2=[PF1^2+PF2^2-F1F2^2]/2PF1PF2=[6^2+2*64-100]/2*64=1/2
sinF1PF2=根号3/2,S△F1PF2=0.5*64*根号3/2=16根号3
===》x^2/9-y^2/16=1,a^2=9,b^2=16,c^2=25,||PF1-PF2|=2a=6,F1F2=2c=10,
CosF1PF2=[PF1^2+PF2^2-F1F2^2]/2PF1PF2=[6^2+2*64-100]/2*64=1/2
sinF1PF2=根号3/2,S△F1PF2=0.5*64*根号3/2=16根号3