Let PQ be a variable focal chord of the parabola y2=4ax where vertex is A. Locus of , centroid of triangle APQ is a parabola P1 then vertex of parabola P1 is,
A
(2a3,0)
No worries! We‘ve got your back. Try BYJU‘S free classes today!
B
(4a3,0)
Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses
C
(8a3,0)
No worries! We‘ve got your back. Try BYJU‘S free classes today!
D
(a3,0)
No worries! We‘ve got your back. Try BYJU‘S free classes today!
Open in App
Solution
The correct option is C(4a3,0)
Let P will be demanded are
P(t)=P(at2,2at)
& Q(t1,2at1)
For focal chord end points
tt1=−1
∴t1=−1t
∴Q(−17)=Q⎛⎜
⎜
⎜⎝at2,−2at⎞⎟
⎟
⎟⎠Let G(α,β) be centroid of △APQ :
α=at2+ot23+o
β=2at+(−2ot)+o3
3αa=t2+1t23β2a=(t−1t)
3αa=(t2+1t2−2)+2
3αα=(t−1t)2+2
3αa=(3β2a)2+2
12αa=9β2+8a2
Replacing α by x & β by y
9y2=12ax−8a2
y2=4ax3−8a29
y2=4a3[x−2a3]
The locus is a parabola with vertex at (=2a3,o) & locus reacts length is 4a3