定比分点公式:如果A(X1,Y1),B(X2,Y2),C分线段AB的比例为是,那么C((X1+SX2)/(1+S),(Y1+SY2)/(1+S))
Q(4cosa,5sina),F(0,3),假设P(X,Y),所以X=(4cosa+2*0)/1+2=4cosa/3,Y=(5sina+2*3)/(1+2)=5sina/3+2,反解,得到sina=3(y-2)/5,cosa=3x/4
(sina)^2+(cosa)^2=1
[3(y-2)/5]^2+(3x/4)^2=1,9(y-2)^2/25+9x^2/16=1,完成.