Question

点P为圆O:x^2+y^2=a^2(a大于0)上一动点,PD垂直x轴于D点,记线段PD的中点M的运动轨迹为曲线C.

Answer 1

1)M(x,y)

xP=xM=x,yP=2y

C:x^2/a^2+y^2(a^2/4)=1

(1/2)*a*a/2=1

a=2