设F1(-c,0),F2(c,0),其中 c^2=a^2-b^2 ,
另设 P(x,y)是椭圆上任一点,
则 PF1=(-c-x ,-y),PF2=(c-x,-y),
所以由 PF1*PF2=(-c-x)(c-x)+(-y)(-y)
=x^2+y^2-c^2
=x^2+b^2(1-x^2/a^2)-c^2
=c^2/a^2*x^2+b^2-c^2
=0
得 x^2=(c^2-b^2)a^2/c^2 ,
由 0
设F1(-c,0),F2(c,0),其中 c^2=a^2-b^2 ,
另设 P(x,y)是椭圆上任一点,
则 PF1=(-c-x ,-y),PF2=(c-x,-y),
所以由 PF1*PF2=(-c-x)(c-x)+(-y)(-y)
=x^2+y^2-c^2
=x^2+b^2(1-x^2/a^2)-c^2
=c^2/a^2*x^2+b^2-c^2
=0
得 x^2=(c^2-b^2)a^2/c^2 ,
由 0