(1)点A,B分别在x,y轴上运动
设A(x,0) B(0,y) P(x0,y0)
|AB|=8
√(x^2+y^2)=8
向量AP=(x0-x,y0) 向量PB=(-x0,y-y0)
向量AP=0.6向量PB
(x0-x,y0)=0.6(-x0,y-y0)
x0-x=-0.6x0
y0=0.6(y-y0)
x=8/5 x0 ①
y=8/3 y0 ②
将①②代入√(x^2+y^2)=8
得 x0^2 /25+ y0^2/9 =16
曲线C的轨迹为椭圆,方程为:x^2/25+y^2/9=1
(2)x^2/25+y^2/9=1
9x^2+25y^2=225 ③
a=5 b=3
c=4
M点是椭圆的右焦点
当PQ⊥ x轴时
P(4,9/5) Q(4,-9/5)
PQ=18/5
S△OPQ=1/2 *OM*PQ=0.5*4* 18/5=36/5
设P(x1,y1) Q(x2,y2)
lPQ的方程为:y=k(x-4)(k存在且k≠ 0)④
将④代入③得:
9x^2+25k^2(x-4)^2=225
化简得:
(25k^+9)x^2 -200k^2 x+400k^2-228=0
x1+x2=200k^2/(25k^+9)
y1+y2=k(x1-4)+k(x2-4)=k(x1+x2)-8k
=200k^3/(25k^+9) -8k
S△OPQ=S△OPM+S△OQM
=1/2 *OM*|y1|+1/2 *OM*|y2|
=1/2 *OM*(|y1|+|y2|)