circles

If ax+by+c=0 is the polar of (1,1) w.r.t the circle x2+y2-2x+2y+1=0 and H.C.F of a,b.c is equal to one then a2+b2+c2= ?

13 Answers

33
Abhishek Priyam ·

I think pole and polar is not in syllabus as far as i know??

11
Shailesh ·

Now the question is what is the polar?!
I dont think u should worry about it.. It is definitely out of syllabus :)

But if u still want, i will tel u what it is !

Syllabus!

Two dimensions: Cartesian coordinates, distance between two points, section formulae, shift of origin.

Equation of a straight line in various forms, angle between two lines, distance of a point from a line; Lines through the point of intersection of two given lines, equation of the bisector of the angle between two lines, concurrency of lines; Centroid, orthocentre, incentre and circumcentre of a triangle.

Equation of a circle in various forms, equations of tangent, normal and chord.

Parametric equations of a circle, intersection of a circle with a straight line or a circle, equation of a circle through the points of intersection of two circles and those of a circle and a straight line.

Equations of a parabola, ellipse and hyperbola in standard form, their foci, directrices and eccentricity, parametric equations, equations of tangent and normal.

62
Lokesh Verma ·

hmm.. well pole and polar are not in syllabus as shailesh and priyam pointed out..

the problem is not very tough as such. Pole and polar are simple concepts.. even simpler for a circle!

33
Abhishek Priyam ·

ok let me see the basic def of it then i'll try it...

it never pays 2 know a thing....

62
Lokesh Verma ·

http://en.wikipedia.org/wiki/Pole_and_polar

read this! it is good enuf to know!

1
skygirl ·

polar eqn: T=0
=> 2x1+2y1 - (x+x1) + (y+y1) +1 =0

here (x1,y1) = (1,1).

putting it... 2 + 2 -1 -x +1+y +1 =0 => -x+y+5=0
then compare this with the eqn of polar given: ax +by +c=0...

a=-1, b=1,c=5 (we will not take muliples of these coz its given that HCF is 1)

so, A^2+B^2+C^2=1+1+25=27... (hope this is the ans... correct me if wrong...)

1
°ღ•๓яυΠ·

we hav pole n polar concept in our syllb

62
Lokesh Verma ·

But not in IIT JEE even though it is not a very difficult question :)

But good that u got ur solution! :)

1
pinky ·

hey...tht's a wrong ans....
a2+b2+c2=5

1
Anika Jain ·

I am wondering. This is in syllabus? i neva heard this!

1
skygirl ·

@pinky,,,, then i dunno... i have given my method as well...

62
Lokesh Verma ·

x2+y2-2x+2y+1=0

The polar will be

xx1+yy1-(x+x1)+(y+y1)+1 where (x1=1 and y1=1)

so this will be

2y+1

compare with ax+by+c=0

a=0, b=2, c=1

so the given expression is 5 :)

1
skygirl ·

oh shit!
wat a shameful mistake .... :(
i wrote the T=0 eqn. wrong.. :( chhi!
and also never noticed it.... chhi!

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