Question from jee

Let C1 and C2 be two cirlces with C2 lying inside C1. A circle C lying inside C1touces C1 internally and C2 externally. Identify the locus of the center of C

12 Answers

11
Anirudh Narayanan ·

62
Lokesh Verma ·

this diagram has solved mostof the problem ;)

1
skygirl ·

nothing else given ?? C2 has no restriction ?

62
Lokesh Verma ·

no!

24
eureka123 ·

aaragon dont u think u have drawn a biased figure..........concentri isn't given

24
eureka123 ·

11
Anirudh Narayanan ·

oopsie.....ya eureka....thanx for pointing out my mistake [4]

24
eureka123 ·

from, RQ+RP=r1+r2 , it looks like locus could be ellipse..............[12][12]

11
Anirudh Narayanan ·

Bhaiya, if C2 were not fixed,,,,won't we get a region more than a locus??

11
Mani Pal Singh ·

sir aaj cam nahin hai

but the concept is

Let the radius of C1 be r1 and circle C2 be r2 and let the center of C1 be at (0,0) and C2 at (h,k)

equation of C1=> x2+y2=r12
equation of C2=> (x-a)2+(y-b)2=r22

let the center of C be (h,k)and be of radius r

so
(h-a)2+(y-b)2=r+r2 =A
(h2+k2)=r1-r =B

So

we can see that A+b = constant

or
PS+PS`=constant
which is the locus of the ellipse at focii (a,b) and (0,0)

1
The Scorpion ·

If C1 and C2 are fixed, then locus of centre of variable circle will b an ellipse (a particular case would be of circle, when given circles are concentric)...

If C1 and C2 are not fixed, then the locus of centre would be a set of infinite ellipse'...

this is a diagramatic guess... i haven't solved anything yet...

let me know if i'm wrong...!!!

62
Lokesh Verma ·

all correct ;)

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