parabola

two mutually perpendicular chords OA and OB are drawn through the vertex O of a parabola y2=4ax. Then the locus of the circumcenter of the triangle OAB...

i got the ans y2=2ax-2a2

is it wrong??? plz reply

5 Answers

62
Lokesh Verma ·

give me a few mins.. u will get the ans..

but to know what is wrong.. i need to know how u reached there!

62
Lokesh Verma ·

seems a straightforward question...

two points be (at12, 2at1) and (at22, 2at2)

let the slope of the first from the origin(vertex) be m, -1/m (bcos perpendicular)

hence, 2at1/at12 = m
2/t1 = m

and

2at2/at22 = -1/m

2/t2 = -1/m

now it should be straighforward...

If u have reached uptil here, then there is some calculation mistake.. but i will finish this question in the next post

62
Lokesh Verma ·

So, we have

t1t2 = - 4

midpoint is given by

{a(t12+t22)/2, a(t1+t2)}

let h,k be the locus...

h=a(t12+t22)/2
k=a(t1+t2)}

2h/a = t12+t22

(k/a)2 = (t1+t2)2
= t12+t22 + 2 t1t2

(k/a)2 = 2h/a -8

Forgive my calculation or step mistakes if any :)

1
skygirl ·

well now i got my mistake...
i took t1.t2=-1... dats y...

1
skygirl ·

thank you :-)

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