设椭圆上的点为(2cosa,√3sina)
PQ^2=(2cosa)^2+(√3sina-1/2)^2
=4cos^2a+3sin^2a-√3sina+1/4
=4-sin^2a-√3sina+1/4
=17/4-(sin^2a+√3sina+3/4-3/4)
=5-(sina+√3/2)^2
因此最大值是当
sina=-√3/2时,为5
设椭圆上的点为(2cosa,√3sina)
PQ^2=(2cosa)^2+(√3sina-1/2)^2
=4cos^2a+3sin^2a-√3sina+1/4
=4-sin^2a-√3sina+1/4
=17/4-(sin^2a+√3sina+3/4-3/4)
=5-(sina+√3/2)^2
因此最大值是当
sina=-√3/2时,为5