由题可知,向量PF1-向量PF2=F2F1,得
PF1^2+PF2^2-2PF1PF2cosθ=4c^2
又PF1-PF2=2a,得PF1^2+PF2^2-2PF1PF2=4a^2
则PF1PF2=2b^2/(1-cosθ)
故其面积为:PF1PF2sinθ=2b^2sinθ/(1-cosθ)(sinθ/(1-cosθ)可进一步化简)
由题可知,向量PF1-向量PF2=F2F1,得
PF1^2+PF2^2-2PF1PF2cosθ=4c^2
又PF1-PF2=2a,得PF1^2+PF2^2-2PF1PF2=4a^2
则PF1PF2=2b^2/(1-cosθ)
故其面积为:PF1PF2sinθ=2b^2sinθ/(1-cosθ)(sinθ/(1-cosθ)可进一步化简)