Topic Question Set


Q 1 :

The locus of the orthocentre of the triangle formed by the lines 

                      (1+p)x-py+p(1+p)=0,

                      (1+q)x-qy+q(1+q)=0,

and y=0, where pq, is                                  [2009]

  • a hyperbola

     

  • a parabola

     

  • an ellipse

     

  • a straight line

     

(4)

The triangle is formed by the lines

AB:(1+p)x-py+p(1+p)=0

AC:(1+q)x-qy+q(1+q)=0

BC:y=0

So that the vertices of ABC are

A(pq,(p+1)(q+1)),  B(-p,0) and C(-q,0)

Let H(h,k) be the orthocentre of ABC. Then as AHBC and passes through A(pq,(p+1)(q+1))

  Equation of AH is x=pq

 h=pq                             ...(i)

   BH is perpendicular to AC

  m1m2=-1k-0h+p×1+qq=-1

kpq+p×1+qq=-1         [using (i)]

  k=-pq                         ...(ii)

From (i) and (ii), we observe that h+k=0

  Locus of (h,k) is x+y=0, which is a straight line.



Q 2 :

Consider a branch of the hyperbola x2-2y2-22x-42y-6=0 with vertex at the point A. Let B be one of the end points of its latus rectum. If C is the focus of the hyperbola nearest to the point A, then the area of the triangle ABC is              [2008]

  • 1-23

     

  • 32-1

     

  • 1+23

     

  • 32+1

     

(2)

Given hyperbola is

x2-2y2-22x-42y-6=0

(x2-22x+2)-2(y2+22y+2)=6+2-4

(x-2)2-2(y+2)2=4

(x-2)222-(y+2)2(2)2=1

 a=2, b=2e=1+24=32

Clearly ABC is a right triangle.

 Area(ABC)=12×AC×BC

=12(ae-a)×b2a

=12(e-1)×b2

=12(32-1)×2

=32-1



Q 3 :

Let a and b be non-zero real numbers. Then, the equation (ax2+by2+c)(x2-5xy+6y2)=0 represents            [2008]

  • four straight lines, when c=0 and a,b are of the same sign.

     

  • two straight lines and a circle, when a=b, and c is of sign opposite to that of a.

     

  • two straight lines and a hyperbola, when a and b are of the same sign and c is of sign opposite to that of a.

     

  • a circle and an ellipse, when a and b are of the same sign and c is of sign opposite to that of a.

     

(2)

  x2-5xy+6y2=0

(x-3y)(x-2y)=0

  x2-5xy+6y2=0 represents a pair of straight lines given by x-3y=0  and  x-2y=0.

Also ax2+by2+c=0 will represent a circle if a=b and c is of sign opposite to that of a.



Q 4 :

A hyperbola, having the transverse axis of length 2sinθ, is confocal with the ellipse 3x2+4y2=12. Then its equation is           [2007]

  • x2cosec2θ-y2sec2θ=1

     

  • x2sec2θ-y2cosec2θ=1

     

  • x2sin2θ-y2cos2θ=1

     

  • x2cos2θ-y2sin2θ=1

     

(1)

The length of transverse axis =2sinθ=2a

a=sinθ

Also the given ellipse is 3x2+4y2=12

x24+y23=1a2=4, b2=3

  e=1-b2a2=1-34=12

   Focus of ellipse =(2×12,0)(1,0)

Since hyperbola is confocal with ellipse, therefore focus of hyperbola

=(1,0)ae=1sinθ×e=1

e=cosecθ

  b2=a2(e2-1)=sin2θ(cosec2θ-1)=cos2θ

   Equation of hyperbola is

     x2sin2θ-y2cos2θ=1

x2cosec2θ-y2sec2θ=1



Q 5 :

If the line 2x+6y=2 touches the hyperbola x2-2y2=4, then the point of contact is       [2004]

  • (-2,6)

     

  • (-5,26)

     

  • (12,16)

     

  • (4,-6)

     

(4)

Equation of tangent to hyperbola x2-2y2=4 at any point (x1,y1) is

xx1-2yy1=4                      ....(i)

But the given tangent is 2x+6y=2

On comparing equation (i) with 2x+6y=2

i.e., 4x+26y=4, we get

x1=4  and  -2y1=26(4,-6) is the required point of contact.



Q 6 :

For hyperbola x2cos2α-y2sin2α=1, which of the following remains constant with change in 'α'                    [2003]

  • abscissae of vertices

     

  • abscissae of foci

     

  • eccentricity

     

  • directrix

     

(2)

Given equation of hyperbola is

x2cos2α-y2sin2α=1a=cosα, b=sinα

e=1+b2a2=1+tan2α=secα

ae=cosα·secα=1       Foci (±1,0)

Hence, foci remain constant with respect to α.



Q 7 :

The equation of the common tangent to the curves y2=8x and xy=-1 is              [2002]

  • 3y=9x+2

     

  • y=2x+1

     

  • 2y=x+8

     

  • y=x+2

     

(4)

Given equation of curves are

y2=8x                    ...(i)

and   xy=-1               ...(ii)

If m is the slope of tangent to (i), then equation of tangent is y=mx+2m

If this tangent is also a tangent to (ii), then putting value of y in curve (ii)

x(mx+2m)=-1mx2+2mx+1=0m2x2+2x+m=0

We should get repeated roots for the equation (condition of tangency)

D=0              (2)2-4m2·m=0 m3=1m=1

Hence equation of required tangent is  y=x+2



Q 8 :

Consider the hyperbola x2100-y264=1 with foci at S and S1, where S lies on the positive x-axis. Let P be a point on the hyperbola, in the first quadrant. Let SPS1=α, with α<π2. The straight line passing through the point S and having the same slope as that of the tangent at P to the hyperbola, intersects the straight line S1P at P1. Let δ be the distance of P from the straight line SP1 and β=S1P. Then the greatest integer less than or equal to βδ9sinα2 is ________.     [2022]



(7)

In S1QP,  sinα2=S1Qβ

S1Q=βsinα2

Product of distances of any tangent from two foci =b2

δ·S1Q=δ×βsinα2=b2 

So,   βδsinα29=b29=649

  [649]=7ss



Q 9 :

The line 2x+y=1 is tangent to the hyperbola x2a2-y2b2=1. If this line passes through the point of intersection of the nearest directrix and the x-axis, then the eccentricity of the hyperbola is ____.           [2010]



(2)

Intersection point of nearest directrix x=ae and x-axis is (ae,0)

Since 2x+y=1 passes through (ae,0),

 2ae=1a=e2

Also y=-2x+1 is a tangent to x2a2-y2b2=1

 1=a2(-2)2-b24a2-b2=1

4a2-a2(e2-1)=14×e24-e24(e2-1)=1

e2=4 as e>1 for hyperbola,  e=2



Q 10 :

Let a and b be positive real numbers such that a>1 and b<a. Let P be a point in the first quadrant that lies on the hyperbola x2a2-y2b2=1. Suppose the tangent to the hyperbola at P passes through the point (1, 0) and suppose the normal to the hyperbola at P cuts off equal intercepts on the coordinate axes. Let Δ denote the area of the triangle formed by the tangent at P, the normal at P and the x-axis. If e denotes the eccentricity of the hyperbola, then which of the following statements is/are TRUE?    [2020]

  • 1<e<2

     

  • 2<e<2

     

  • Δ=a4

     

  • Δ=b4

     

Select one or more options

(1, 4)

Let P(a secθ, b tanθ)

Equation of tangent at P

xasecθ-ybtanθ=1

  (1,0) lies on the tangent

so a=secθ

Equation of normal at P

axsecθ+bytanθ=a2+b2

since normal at P makes equal intercept on co-ordinate axes,

 Slope of normal is -1

so  -absinθ=-1

b=tanθ,  hence, a2-b2=1                   ...(i)

  e=1+b2a2=1+a2-1a2=2-1a2                    from (i)

Since a>1, so e(1,2)

Hence, option (1) is true.

Area of PAB=12AP·PB

=12(a2-1)2+(b2)2×2b4

=122b42b4=b4    from (i)

Hence, option (4) is true.



Q 11 :

If 2x-y+1=0 is a tangent to the hyperbola x2a2-y216=1, then which of the following cannot be sides of a right angled triangle?            [2017]

  • a,4,1

     

  • a,4,2

     

  • 2a,8,1

     

  • 2a,4,1

     

Select one or more options

(1, 2, 3)

Given 2x-y+1=0  i.e.  y=2x+1 is a tangent to hyperbola x2a2-y216=1

  c2=a2m2-b2

12=a2×22-16

a2=174a=172

  a,4,1; a,4,2; 2a,8,1  i.e.  172,4,1;   172,4,2;   17,8,1 cannot be the sides of a right triangle.



Q 12 :

Consider the hyperbola H:x2-y2=1 and a circle S with center N(x2,0). Suppose that H and S touch each other at a point P(x1,y1) with x1>1 and y1>0. The common tangent to H and S at P intersects the x-axis at point M. If (l,m) is the centroid of the triangle PMN, then the correct expression(s) is/are         [2015]

  • dldx1=1-13x12 for x1>1  

     

  • dmdx1=x13(x12-1) for x1>1  

     

  • dldx1=1+13x12 for x1>1  

     

  • dmdy1=13 for y1>0  

     

Select one or more options

(1, 2, 4)

H: x2-y2=1 is a hyperbola and S: Circle with centre N(x2,0). Common tangent to H and S at P(x1,y1) is

      xx1-yy1=1m1=x1y1

Now, radius of circle S with centre N(x2,0) through the point of contact (x1,y1) is perpendicular to the tangent.

  m1m2=-1x1y1×0-y1x2-x1=-1

x2=2x1

  M is the point of intersection of tangent at P and x-axis.

  M(1x1,0)    Centroid of PMN is (,m)

 x1+1x1+x2=3  and  y1=3m

13(3x1+1x1)=  and  y13=m    [x2=2x1]

  ddx1=1-13x12,    dmdy1=13

Also (x1,y1) lies on H,   x12-y12=1 y1=x12-1

 m=13x12-1        dmdx1=x13x12-1



Q 13 :

Tangents are drawn to the hyperbola x29-y24=1, parallel to the straight line 2x-y=1. The points of contact of the tangents on the hyperbola are             [2012]

  • (922,12)

     

  • (-922,-12)

     

  • (33,-22)

     

  • (-33,22)

     

Select one or more options

(1, 2)

If slope of tangents to hyperbola x2a2-y2b2=1 is m, then equation of tangent to the hyperbola is

y=mx±a2m2-b2 with the points of contact (±a2ma2m2-b2,±b2a2m2-b2)

  Tangent to hyperbola x29-y24=1 is parallel to 2x-y=1

  Slope of tangent=2

 Points of contact are (±9×29×4-4,±49×4-4)

i.e.  (922,12)  and  (-922,-12)



Q 14 :

Let the eccentricity of the hyperbola x2a2-y2b2=1 be reciprocal to that of the ellipse x2+4y2=4. If the hyperbola passes through a focus of the ellipse, then       [2011]

  • the equation of the hyperbola is x23-y22=1

     

  • a focus of the hyperbola is (2,0)

     

  • the eccentricity of the hyperbola is 53

     

  • the equation of the hyperbola is x2-3y2=3

     

Select one or more options

(2, 4)

Given ellipse x2+4y2=4x24+y21=1

Its focus is (±3,0) and eccentricity, e=1-14=32

Given hyperbola x2a2-y2b2=1

Its eccentricity is 1+b2a2

According to the question, 1+b2a2=23ba=13

As hyperbola passes through the eccentricity of the ellipse (±3,0)

  3a2=1 or a=3        b=1 and focus of hyperbola  (±2,0)

  Equation of hyperbola is x23-y21=1x2-3y2=3



Q 15 :

An ellipse intersects the hyperbola 2x2-2y2=1 orthogonally. The eccentricity of the ellipse is reciprocal of that of the hyperbola. If the axes of the ellipse are along the coordinate axes, then                   [2009]

 

  • equation of ellipse is x2+2y2=2

     

  • the foci of ellipse are (±1,0)

     

  • equation of ellipse is x2+2y2=4

     

  • the foci of ellipse are (±2,0)

     

Select one or more options

(1, 2)

The given hyperbola is

x2-y2=12            ...(i)

which is a rectangular hyperbola  (a=b)     e=2

Let the ellipse be x2a2+y2b2=1

Its eccentricity =12

  b2=a2(1-12)  b2=a22

Hence, the equation of ellipse becomes

x2+2y2=a2                  ...(ii)

Let the hyperbola (i) and ellipse (ii) intersect each other at P(x1,y1)

Then slope of hyperbola (i) at P is given by

    m1=(dydx)(x1,y1)=x1y1

and that of ellipse (ii) at P is

m2=(dydx)(x1,y1)=-x12y1

As the two curves intersect orthogonally,

  m1m2=-1

x1y1(-x12y1)=-1x12=2y12             ...(iii)

Also P(x1,y1) lies on x2-y2=12

  x12-y12=12                 ...(iv)

On solving (iii) and (iv), we get y12=12 and  x12=1

Also P(x1,y1) lies on ellipse x2+2y2=a2

 x12+2y12=a21+1=a2 or a2=2

 Equation of required ellipse is x2+2y2=2, whose foci are (±ae,0)=(±2×12,0)=(±1,0)



Q 16 :

Let a hyperbola passes through the focus of the ellipse x225+y216=1. The transverse and conjugate axes of this hyperbola coincide with the major and minor axes of the given ellipse, also the product of eccentricities of given ellipse and hyperbola is 1, then                      [2006]

  • the equation of hyperbola is x29-y216=1

     

  • the equation of hyperbola is x29-y225=1

     

  • focus of hyperbola is (5,0)

     

  • vertex of hyperbola is (53,0)

     

Select one or more options

(1, 3)

For the given ellipse x225+y216=1e=1-1625=35

Eccentricity of hyperbola =53

Let the hyperbola be x2A2-y2B2=1 then

B2=A2(259-1)=169A2      x2A2-9y216A2=1

As it passes through focus of ellipse i.e. (3,0)

  we get A2=9B2=16

  Equation of hyperbola is x29-y216=1

Its focus is (5, 0) and vertex is (3, 0)



Q 17 :

Let H:x2a2-y2b2=1, where a>b>0, be a hyperbola in the xy-plane whose conjugate axis LM subtends an angle of 60° at one of its vertices N. Let the area of the triangle LMN be 43.                 [2018]

  List I   List II
P. The length of the conjugate axis of H is 1. 8
Q. The eccentricity of H is 2. 43
R. The distance between the foci of H is 3. 23
S. The length of the latus rectum of H is 4. 4

 

The correct option is:

  • P → 4; Q → 2; R → 1; S → 3

     

  • P → 4; Q → 3; R → 1; S → 2

     

  • P → 4; Q → 1; R → 3; S → 2

     

  • P → 3; Q → 4; R → 2; S → 1

     

(2)

Area of LMN=43    (given)

12×LM×ON=4312(2b)(3b)=43

 b2=4b=2

So, length of the conjugate axis of hyperbola =2b=4

Now, tan30°=OLON=baa=3ba=23

 b2=a2(e2-1)4=12(e2-1)e2=1+13=43

 The eccentricity of hyperbola e=23

The distance between the foci of hyperbola=2ae

=2×23×23=8

And length of latus rectum of hyperbola

=2b2a=2×423=43



Q 18 :

By appropriately matching the information given in the three columns of the following table. Column 1, 2, and 3 contain conics, equations of tangents to the conics and points of contact, respectively.                                 [2017]

  Column 1   Column 2   Column 3
(I) x2+y2=a2 (i) my=m2x+a (P) (am2,2am)
(II) x2+a2y2=a2 (ii) y=mx+am2+1 (Q) (-mam2+1,am2+1)
(III) y2=4ax (iii) y=mx+a2m2-1 (R) (-a2ma2m2+1,1a2m2+1)
(IV) x2-a2y2=a2 (iv) y=mx+a2m2+1 (S) (-a2ma2m2-1,-1a2m2-1)

 

Q.   For a=2, if a tangent is drawn to a suitable conic (Column 1) at the point of contact (-1,1), then which of the following options is the only correct combination for obtaining its equation?

  • (I)(i)(P)

     

  • (I)(ii)(Q)

     

  • (II)(ii)(Q)

     

  • (III)(i)(P)

     

(2)

For a=2 and point of contact (-1,1)

Equation of circle is satisfied

          x2+y2=2

then equation of tangent is

    -x+y=2m=1 and point of contact

(-mam2+1,am2+1)=(-22,22)=(-1,1)

 (I),(ii),(Q) is the correct combination.



Q 19 :

By appropriately matching the information given in the three columns of the following table. Column 1, 2, and 3 contain conics, equations of tangents to the conics and points of contact, respectively.             [2017]

  Column 1   Column 2   Column 3
(I) x2+y2=a2 (i) my=m2x+a (P) (am2,2am)
(II) x2+a2y2=a2 (ii) y=mx+am2+1 (Q) (-mam2+1,am2+1)
(III) y2=4ax (iii) y=mx+a2m2-1 (R) (-a2ma2m2+1,1a2m2+1)
(IV) x2-a2y2=a2 (iv) y=mx+a2m2+1 (S) (-a2ma2m2-1,-1a2m2-1)

 

Q.    If a tangent to a suitable conic (column 1) is found to be y=x+8 and its point of contact is (8, 16), then which of the following options is the only correct combination?

  • (I)(ii)(Q)

     

  • (II)(iv)(R)

     

  • (III)(i)(P)

     

  • (III)(ii)(Q)

     

(3)

Tangent y=x+8m=1 Point (8,16)

 Both the coordinates as well as m, are positive. The only possibility of point is (am2,2am)=(8,16)    a=8

Also it satisfies the equation of curve y2=4ax for the point (8,16)

And equation of tangent my=m2x+a is satisfied by m=1 and a=8

 (III),(i),(P) is the correct combination.



Q 20 :

By appropriately matching the information given in the three columns of the following table. Column 1, 2, and 3 contain conics, equations of tangents to the conics and points of contact, respectively.                     [2017]

  Column 1   Column 2   Column 3
(I) x2+y2=a2 (i) my=m2x+a (P) (am2,2am)
(II) x2+a2y2=a2 (ii) y=mx+am2+1 (Q) (-mam2+1,am2+1)
(III) y2=4ax (iii) y=mx+a2m2-1 (R) (-a2ma2m2+1,1a2m2+1)
(IV) x2-a2y2=a2 (iv) y=mx+a2m2+1 (S) (-a2ma2m2-1,-1a2m2-1)

 

Q.    The tangent to a suitable conic (Column 1) at (3,12) is found to be 3x+2y=4, then which of the following options is the only correct combination?

  • (IV)(iii)(S)

     

  • (IV)(iv)(S)

     

  • (II)(iii)(R)

     

  • (II)(iv)(R)

     

(4)

Point of contact (3,12) and tangent 3x+2y=4

 m=-32

 Both the coordinates are positive and m is negative.

The possibilities for points are

Q(-mam2+1,am2+1)

or  R(-a2ma2m2+1,1a2m2+1)

For point Q (3a7,2a7)=(3,12)

We get a=7 and a=74, which is not possible.

For point R(a233a2+4,23a2+4)=(3,12)

a23a2+4=1 and 23a2+4=12

a4-3a2-4=0 and 3a2=12

 a2=4

Also for a2=4, equation of ellipse

x2+a2y2=a2 is satisfied for the point (3,12)

 II, (iv), R is the correct combination.



Q 21 :

Match the conics in Column I with the statements/expressions in Column II.                     [2009]

  Column I   Column II
(A) Circle (p) The locus of the point (h,k) for which the line hx+ky=1 touches the circle x2+y2=4
(B) Parabola (q) Points z in the complex plane satisfying |z+2|-|z-2|=±3
(C) Ellipse (r) Points of the conic have parametric representation x=3(1-t21+t2), y=2t1+t2
(D) Hyperbola (s) The eccentricity of the conic lies in the interval 1x<
    (t) Points z in the complex plane satisfying Re(z+1)2=|z|2+1

 

  • A(p);  B(s,t);  C(r);  D(q,s)

     

  • A(q,s);  B(s,t);  C(r);  D(p)

     

  • A(q,s);  B(r);  C(s,t);  D(p)

     

  • A(r);  B(q,s);  C(s,t);  D(p)

     

(1)

(p) As the line hx+ky=1, touches the circle x2+y2=4

 Length of perpendicular from centre (0,0) of circle to the line=radius of the circle

1h2+k2=2 h2+k2=14

 Locus of (h,k) is x2+y2=14, which is a circle.

(q) We know that if |z-z1|-|z-z2|=k,

where |k|<|z1-z2|, then z traces a hyperbola.

Here |z+2|-|z-2|=±3

 Locus of z is a hyperbola.

(r) Given : x=3(1-t21+t2),  y=2t1+t2

x3=1-t21+t2 and y=2t1+t2

On squaring and adding, we get

x23+y2=(1-t2)2+4t2(1+t2)2=1x23+y21=1

which is the equation of an ellipse.

(s) We know, eccentricity of a parabola =1

       and eccentricity of an ellipse <1

       and eccentricity of a hyperbola >1.

 Hence, the conics whose eccentricity lies in 1x< are parabola and hyperbola.

(t) Let z=x+iy

 Re[(x+1)+iy]2=x2+y2+1

(x+1)2-y2=x2+y2+1

  y2=x, which is a parabola.



Q 22 :

Match the statements in Column I with the properties in Column II and indicate your answer by darkening the appropriate bubbles in the 4×4 matrix given in the ORS.      [2007]

  Column I   Column II
(A) Two intersecting circles (p) have a common tangent
(B) Two mutually external circles (q) have a common normal
(C) Two circles, one strictly inside the other (r) do not have a common tangent
(D) Two branches of a hyperbola (s) do not have a common normal

 

  • (A)(q,r);    (B)(p,q);    (C)(q,r);    (D)(p,q)

     

  • (A)(p,q);    (B)(p,q);    (C)(q,r);    (D)(q,r)

     

  • (A)(q,r);    (B)(q,r);    (C)(p,q);    (D)(p,q)

     

  • (A)(p,q);    (B)(p,q);    (C)(q,r);    (D)(q,r)

     

(2)

(A) - p,q

It is clear from the figure that two intersecting circles have a common tangent and a common normal joining the centres.

(B) - p,q

(C) - q,r

Two circles, when one is strictly inside the other, have a common normal C1C2 but no common tangent.

(D) - q,r

Two branches of hyperbola have no common tangent but have a common normal joining S1S2.



Q 23 :

The circle x2+y2-8x=0 and hyperbola x29-y24=1 intersect at the points A and B.                     [2010]

Q.     Equation of the circle with AB as its diameter is

  • x2+y2-12x+24=0

     

  • x2+y2+12x+24=0

     

  • x2+y2+24x-12=0

     

  • x2+y2-24x-12=0

     

(1)

Given a circle

x2+y2-8x=0            ...(i)

and a hyperbola 4x2-9y2-36=0        ...(ii)

To find their point of intersection, substitute the value of y2 from equation (i) in equation (ii), we get

4x2-9(8x-x2)=3613x2-72x-36=0

x=6,-613y2=12,-4813-36169    (not possible)

 (6,23) and (6,-23) are points of intersection.

 Equation of required circle is

(x-6)(x-6)+(y-23)(y+23)=0

x2+y2-12x+24=0



Q 24 :

The circle x2+y2-8x=0 and hyperbola x29-y24=1 intersect at the points A and B.                [2010]

Q.    Equation of a common tangent with positive slope to the circle as well as to the hyperbola is

  • 2x-5y-20=0

     

  • 2x-5y+4=0

     

  • 3x-4y+8=0

     

  • 4x-3y+4=0

     

(2)

Any tangent to x29-y24=1 is xsecα3-ytanα2=1

It touches circle with center (4,0) and radius =4

 4secα-33sec2α9+tan2α4=4

16sec2α-24secα+9=144(sec2α9+tan2α4)

12sec2α+8secα-15=0secα=56 or -32

since secα=56<1 is not possible.

 secα=-32tanα=±52

 Slope of tangent=2secα3tanα=2(-3/2)3(-5/2)=25      (for +ve value of tanα)

 Equation of tangent is -x2+y54=1

2x-5y+4=0