MEDIUM
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Given three collinear points A(3, 1), B(7, -1) and C(5, 0). The length of a tangent drawn from A to any circle that passes through B and C is ___ units.

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Important Questions on Circle

HARD
The angle between a pair of tangents drawn from a point P to the circle x2+y2+4x-6y+9sin2α+13cos2α=0 is 2α. The equation of the locus of the point P is
MEDIUM
If the chord Ly-mx-1=0 of the circle Sx2+y2-1=0 touches the circle S1=x2+y2-4x+1=0, then the possible points for which L=0 is a chord of contact of S=0 are
HARD
If the lines 2x+y+12=0, kx-3y-10=0 are conjugate with respect to the circle x2+y2-4x+3y-1=0, then k=
HARD
Let T be a circle with diameter AB and centre O. Let l be the tangent to T at B. For each point M on T different from A, consider the tangent t at M and let interest l at P. Draw a line parallel to AB through P intersecting OM at Q. The locus of Q as M varies over T is
HARD
If the chord of contact of tangents from a point on the circle x2+y2=r12 to the circle x2+y2=r22 touches the circle x2+y2=r32, then r1, r2, r3 are in:
MEDIUM
Let A be the centre of the circle x2+y2-2x-4y-20=0. Let B(1, 7) and D(4,-2) be two points on the circle such that tangents at B and D meet at C. The area of the quadrilateral ABCD is
HARD
The lines represented by 5x2-xy-5x+y=0 are normals to a circle S=0. If this circle touches the circle S'x2+y2-2x+2y-7=0 externally, then the equation of the chord of contact of centre of S'=0 with respect to S=0 is
MEDIUM
x2+y2-4x-2y-11=0 is a circle to which tangents are drawn from the point 4,5 which form a quadrilateral with a pair of radii. The area of this quadrilateral in square units is ___________.
MEDIUM
The angle between the pair of tangents drawn from 1,3 to the circle x2+y2-2x+4y-11=0 is
MEDIUM
The area (in sq. units) of the triangle formed by the two tangents drawn from the extremal point O0,0 to the circle x2+y2-2 gx-2hy+h2=0 and their chord of contact is
HARD
If Px1,y1 is a point such that the lengths of the tangents from it to the circles x2+y2-4x-6y-12=0 and x2+y2+6x+18y+26=0 are in the ratio 2:3, then the locus of P is
HARD
A line drawn through the point P4,7 cuts the circle x2+y2=9 at the points A and B. Then PA·PB is equal to.
HARD
Two tangents are drawn from a point P to the circle x2+y2-2x-4y+4=0, such that the angle between these tangents is tan-1125, where tan-1125(0,π). If the centre of the circle is denoted by C and these tangents touch the circle at points A and B, then the ratio of the areas of ΔPAB and ΔCAB is :
MEDIUM
A chord AB is drawn from the point A(0, 3) on the circle x2+4x+(y-3)2=0, and is extended to M such that AM=2 AB. The locus of M is
HARD
The area of the quadrilateral formed by the tangents from the point 4,7 with a pair of radii of the circle x2+y2-4x-6y-3=0 is
EASY
The locus of the mid points of the chords of the circle x2-2x+y2=0 drawn from a point 0, 0 on it is
MEDIUM
The polars of -1, 2 with respect to the two circles S1x2+y2+6y+7=0 and S2x2+y2+6x+1=0 are
MEDIUM
Consider the circles
S1: x2+y2+2x+8y-23=0 and S2: x2+y2-4x+10y+19=0
If the polars of the centre of a circle with respect to the another circle are L1 and L2, then L1, L2 are
MEDIUM
If the length of the tangent from any point on the circle x-32+y+22=5r2 to the circle x-32+y+22=r2 is 16 units, then the area between the two circles in sq. units is
MEDIUM
Let A be the centre of the circle x2+y2-2x-4y-20=0, and B1,7 and D(4,2) are points on the circle then, if tangents be drawn at B and D, which meet at C, then area of quadrilateral ABCD is