# Thread: parametrics and focal chord

1. ## parametrics and focal chord

pls help rip
P(2at,at^2) is a point on the parabola x^2=4ay. S is the focus, T is the foot of the perpendicular frpm P to the directrix, and A is the point where the tangent at P meets the y aixs.
(i) write down the coordinates of T
(ii) show that A is the point (0, -at^2)
(iii) what is point S

2. ## Re: parametrics and focal chord

Originally Posted by sssona09
pls help rip
P(2at,at^2) is a point on the parabola x^2=4ay. S is the focus, T is the foot of the perpendicular frpm P to the directrix, and A is the point where the tangent at P meets the y aixs.
(i) write down the coordinates of T
(ii) show that A is the point (0, -at^2)
(iii) what is point S
I'll just give hints

i) Use formula sheet for the normal equation as it says perpendicular at P and sub y = -a as that is the directrix equation

ii) Use tangent equation on formula sheet and sub x = 0

iii) (0, a) as it is the focus

3. ## Re: parametrics and focal chord

Originally Posted by pikachu975
I'll just give hints

i) Use formula sheet for the normal equation as it says perpendicular at P and sub y = -a as that is the directrix equation

ii) Use tangent equation on formula sheet and sub x = 0

iii) (0, a) as it is the focus
ohh thank youuuu pikachu

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