Topic Question Set


Q 1 :

Let S denote the locus of the point of intersection of the pair of lines 4x-3y=12α, 4αx+3αy=12, where α varies over the set of non-zero real numbers. Let T be the tangent to S passing through the points (p,0) and (0,q), q>0 and parallel to the line 4x-32y=0. Then the value of pq is               [2025]

  • -62

     

  • -32

     

  • -92

     

  • -122

     

(1)

4x-3y=12α    ...(i)

 4x+3y=12α    ...(ii)

For elimination of α, multiply equations (i) and (ii)

16x2-9y2=144x29-y216=1  (Hyperbola)

Since, T is parallel to 4x-3y2=0

m=43/2=423

So equation of tangent:

y=mx+a2m2-b2  as q>0

y=423x+9×16×29-16

y=42x3+4(p,0)0=42p3+4p=-32

and (0,q)q=4;    pq=-32×4=-62



Q 2 :

Consider the ellipse x29+y24=1. Let S(p,q) be a point in the first quadrant such that p29+q24>1. Two tangents are drawn from S to the ellipse, of which one meets the ellipse at one end point of the minor axis and the other meets the ellipse at a point T in the fourth quadrant. Let R be the vertex of the ellipse with positive x-coordinate and O be the center of the ellipse. If the area of the triangle ORT is 32, then which of the following options is correct?               [2024]

  • q=2, p=33

     

  • q=2, p=43

     

  • q=1, p=53

     

  • q=1, p=63

     

(1)

Given that p29+q24>1 then S(p,q) lies outside the ellipse

SA is tangentq=2

Area of ORT=32

|12×OR×QT|=32|12×3×β|=32β=-1

  α29+β24=1α29=1-14=34

α2=274α=332

Tangent at T

T=0

x·3329+y(-1)4=1|(p,2)

p36-12=1p36=32p=33

  p=33, q=2



Q 3 :

The ellipse E1:x29+y24=1 is inscribed in a rectangle R whose sides are parallel to the coordinate axes. Another ellipse E2 passing through the point (0, 4) circumscribes the rectangle R. The eccentricity of the ellipse E2 is                    [2012]

  • 22

     

  • 32

     

  • 12

     

  • 34

     

(3)

As rectangle ABCD circumscribes the ellipse x29+y24=1,

  A=(3,2)

Let the ellipse circumscribing the rectangle ABCD is x2a2+y2b2=1    ...(i)

Given that ellipse (i) passes through (a,4)b2=16

Also ellipse (i) passes through A(3,2)

  9a2+416=19a2=1-14=34

a2=12

  e=1-b2a2=1-1216=14=12



Q 4 :

The normal at a point P on the ellipse x2+4y2=16 meets the x-axis at Q. If M is the midpoint of the line segment PQ, then the locus of M intersects the latus rectums of the given ellipse at the points              [2009]

  • (±352,±27)

     

  • (±352,±194)

     

  • (±23,±17)

     

  • (±23,±437)

     

(3)

Given ellipse is x242+y222=1

  a2=16, b2=4e2=1-416=34e=32

Let P(4cosθ,2sinθ) be any point on the ellipse, then equation of normal at P is

4xsinθ-2ycosθ=12sinθcosθ

x3cosθ-y6sinθ=1

  Q, the point where normal at P meets x-axis, has coordinates (3cosθ,0)

  Mid point of PQ is M(7cosθ2,sinθ)

For locus of point M we consider

x=7cosθ2,  y=sinθcosθ=2x7,  sinθ=y

Since sin2θ+cos2θ=1

  4x249+y2=1    ...(i)

Also the latus rectum of given ellipse is

x=±ae=±4×32x=±23    ...(ii)

On solving equations (i) and (ii), we get

4×1249+y2=1y2=149 or y=±17

  The required points are (±23,±17).



Q 5 :

The line passing through the extremity A of the major axis and extremity B of the minor axis of the ellipse x2+9y2=9 meets its auxiliary circle at the point M. Then the area of the triangle with vertices at A,M and the origin O is                 [2009]

  • 3110

     

  • 2910

     

  • 2110

     

  • 2710

     

(4)

Given ellipse is x2+9y2=9 x232+y212=1

  Coordinates of A and B are (3,0) and (0,1) respectively

  Equation of AB is x3+y1=1

x+3y-3=0    ...(i)

and equation of auxiliary circle of given ellipse is

x2+y2=9    ...(ii)

On solving equations (i) and (ii), we get the point M where line AB meets the auxiliary circle.

Putting x=3-3y from (i) in (ii), we get

     (3-3y)2+y2=9

9-18y+9y2+y2=910y2-18y=0

y=0, 95  x=3,-125

Clearly M(-125,95)

  Area of OAM=12|001301-125951|=2710



Q 6 :

The minimum area of triangle formed by the tangent to the ellipse x2a2+y2b2=1 and coordinate axes is                  [2005]

  • ab sq. units

     

  • a2+b22 sq. units

     

  • (a+b)22 sq. units

     

  • a2+ab+b23 sq. units

     

(1)

Any tangent to the ellipse x2a2+y2b2=1  at P(acosθ,bsinθ) is xcosθa+ysinθb=1

It meets coordinate axes at A(asecθ,0) and B(0,bcosecθ)

  Area of OAB=12×asecθ×bcosecθ=absin2θ

For area of OAB to be minimum, sin2θ should be maximum, i.e., 1

  Minimum area of OAB=ab sq. units.



Q 7 :

If tangents are drawn to the ellipse x2+2y2=2, then the locus of the mid-point of the intercept made by the tangents between the coordinate axes is        [2004]

  • 12x2+14y2=1

     

  • 14x2+12y2=1

     

  • x22+y24=1

     

  • x24+y22=1

     

(1)

Any tangent to ellipse x22+y21=1 is

xcosθ2+ysinθ=1 which makes intercept AB between the coordinate axes.

 A(2secθ,0),  B(0,cosecθ)

If (h,k) be the mid-point of AB, then

      2h=2secθ,  2k=cosecθ

cosθ=12h,  sinθ=12k

Now cos2θ+sin2θ=1

(12h)2+(12k)2=112h2+14k2=1

  Required locus is 12x2+14y2=1



Q 8 :

The area of the quadrilateral formed by the tangents at the end points of latus rectum to the ellipse x29+y25=1, is                [2003]

  • 274 sq. units

     

  • 9 sq. units

     

  • 272 sq. units

     

  • 27 sq. units

     

(4)

Given equation of ellipse is x29+y25=1

  a2=9, b2=5e=1-59=23

  End point of latus rectum in first quadrant is L(2,53)

Equation of tangent at L is 2x9+y3=1, which meets x-axis at A(92,0) and y-axis at B(0,3)

  Area of OAB=12×92×3=274

Now by symmetry area of quadrilateral ABCD

=4×Area(OAB)=4×274=27 sq. units.



Q 9 :

Suppose that the foci of the ellipse x29+y25=1 are (f1,0) and (f2,0) where f1>0 and f2<0. Let P1 and P2 be two parabolas with a common vertex at (0, 0) and with foci at (f1,0) and (2f2,0), respectively. Let T1 be a tangent to P1 which passes through (2f2,0) and T2 be a tangent to P2 which passes through (f1,0). If m1 is the slope of T1 and m2 is the slope of T2, then the value of (1m12+m22) is                      [2015]



(4)

Given: Ellipse is x29+y25=1

a=3, b=5, e=23f1=2, f2=-2

P1: y2=8x  and  P2: y2=-16x

T1: y=m1x+2m1

It passes through (-4,0),    0=-4m1+2m1m12=12

T2: y=m2x-4m2, It passes through (2,0)

 0=2m2-4m2m22=2

  1m12+m22=2+2=4

 



Q 10 :

A vertical line passing through the point (h,0) intersects the ellipse x24+y23=1 at the points P and Q. Let the tangents to the ellipse at P and Q meet at the point R. If Δ(h) is the area of the triangle PQR, Δ1=max1/2h1Δ(h)  and  Δ2=min1/2h1Δ(h), then 85Δ1-8Δ2=                 [2013]



(9)

Vertical line x=h, meets the ellipse x24+y23=1 at

P(h,324-h2) and Q(h,-324-h2)

By symmetry, tangents at P and Q will meet each other at x-axis.

Tangent at P is xh4+y364-h2=1, which meets x-axis at R(4h,0)

area (PQR)=12×34-h2×(4h-h)

Let Δ(h)=3(4-h2)3/22h

dΔdh=-3[4-h2(h2+2)h2]<0

  Δ(h) is a decreasing function.

  12h1Δmax=Δ(12) and Δmin=Δ(1)

  Δ1=Δmax=32·(4-14)3/212=4585  and Δ2=Δmin=3·332·1=92

  85Δ1-8Δ2=45-36=9



Q 11 :

Let E be the ellipse x216+y29=1. For any three distinct points P,Q and Q' on E, let M(P,Q) be the midpoint of the line segment joining P and Q, and M(P,Q') be the midpoint of the line segment joining P and Q'. Then the maximum possible value of the distance between M(P,Q) and M(P,Q'), as P,Q and Q' vary on E, is ______.                            [2021]



(4)

Let A and B be midpoints of segment PQ and PQ' respectively

By midpoint theorem

ABQQ' and AB=12QQ'

  Distance between M(P,Q) and M(P,Q')=12QQ'

Since, Q,Q' must be on E, so, maximum of QQ'=8

  Maximum of AB=82=4



Q 12 :

Let P(x1,y1) and Q(x2,y2) be two distinct points on the ellipse x29+y24=1 such that y1>0 and y2>0. Let C denote the circle x2+y2=9, and M be the point (3, 0). Suppose the line x=x1 intersects C at R, and the line x=x2 intersects C at S, such that the y-coordinates of R and S are positive. Let ROM=π6 and SOM=π3, where O denotes the origin (0, 0). Let |XY| denote the length of the line segment XY.

Then which of the following statement(s) is (are) TRUE?                     [2025]

  • The equation of the line joining P and Q is 2x+3y=3(1+3)

     

  • The equation of the line joining P and Q is 2x+y=3(1+3)

     

  • If N2=(x2,0), then 3|N2Q|=2|N2S|

     

  • If N1=(x1,0), then 9|N1P|=4|N1R|

     

Select one or more options

(1, 3)

mPQ=3-132(1-3)=-23

So, equation of PQ is 2x+3y=3+33

2x+3y=3(1+3)

3|N2Q|=2|N2S|3×3=2×332

9|N1P|=4|N1R|9×1=4×32



Q 13 :

Let T1 and T2 be two distinct common tangents to the ellipse E: x26+y23=1 and the parabola P: y2=12x. Suppose that the tangent T1 touches P and E at the points A1 and A2, respectively, and the tangent T2 touches P and E at the points A4 and A3, respectively. Then which of the following statement(s) is (are) true?    [2023]

  • The area of the quadrilateral A1A2A3A4 is 35 square units

     

  • The area of the quadrilateral A1A2A3A4 is 36 square units

     

  • The tangents T1 and T2 meet the x-axis at the point (-3,0)

     

  • The tangents T1 and T2 meet the x-axis at the point (-6,0)

     

Select one or more options

(1, 3)

Given equation of ellipse E: x26+y23=1.

Tangent: y=m1x±6m12+3

Equation of parabola P: y2=12x

Tangent: y=m2x+3m2

For common tangent

m1=m2=m (say) and ±6m12+3=3m2

m=±1

Equation of common tangents are

T1: y=x+3  and  T2: y=-x-3.

   point of contact for parabola is (am2,2am)

A1(3,6) and A4(3,-6) on solving y=x+3 or y=-x-3 and

      equation of ellipse x26+y23=1 we get A2(-2,1) and A3(-2,-1).

Area of quadrilateral A1A2A3A4=12(12+2)×5

( A1A4=12, A2A3=2, MN=5)

=35 sq. units.

Put y=0 in T1 and T2 we get point of intersection with x-axis is (-3,0).

Hence option (1) and (3) are correct.



Q 14 :

Consider two straight lines, each of which is tangent to both the circle x2+y2=12 and the parabola y2=4x. Let these lines intersect at the point Q. Consider the ellipse whose center is at the origin O(0,0) and whose semi-major axis is OQ. If the length of the minor axis of this ellipse is 2, then which of the following statement(s) is (are) TRUE?                               [2018]

  • For the ellipse, the eccentricity is 12 and the length of the latus rectum is 1

     

  • For the ellipse, the eccentricity is 12 and the length of the latus rectum is 12

     

  • The area of the region bounded by the ellipse between the lines x=12 and x=1 is 142(π-2)

     

  • The area of the region bounded by the ellipse between the lines x=12 and x=1 is 116(π-2)

     

Select one or more options

(1, 3)

Let the equation of common tangent is y=mx+1m

  |0+0+1m1+m2|=12

m4+m2-2=0m=±1

 Equation of common tangents are

       y=x+1 and y=-x-1    Q(-1,0)

 Equation of ellipse is x21+y21/2=1

(1)  e=1-12=12 and latus rectum =2b2a=2(12)21=1

(3)  

        Required area=21/21121-x2dx

        =2[x21-x2+12sin-1x]1/21

         =2[π4-(14+π8)]=2(π8-14)=π-242



Q 15 :

Let E1 and E2 be two ellipses whose centers are at the origin. The major axes of E1 and E2 lie along the x-axis and the y-axis, respectively. Let S be the circle x2+(y-1)2=2. The straight line x+y=3 touches the curves S, E1 and E2 at P, Q and R respectively. Suppose that PQ=PR=223. If e1 and e2 are the eccentricities of E1 and E2, respectively, then the correct expression(s) is (are)                     [2015]

  • e12+e22=4340

     

  • e1e2=7210

     

  • |e12-e22|=58

     

  • e1e2=34

     

Select one or more options

(1, 2)

Let E1: x2a2+y2b2=1, where a>b    (i)

and E2: x2c2+y2d2=1, where c<d    (ii)

Also S: x2+(y-1)2=2    (iii)

Tangent at P(x1,y1) to (iii) is x+y=3    (iv)

On solving (iii) and (iv), we get the point of contact P(1,2)

Now, equation of tangent in parametric form,

x-1-12=y-212=±223x=13 or 53 and y=83 or 43

 Q(53,43) and R(13,83)

Now, equation of tangent to E1 at Q is

5x3a2+4y3b2=1 which is identical to x3+y3=1

a2=5 and b2=4e12=1-45=15

And equation of tangent to E2 at R is

x3c2+8y3d2=1, which is identical to x3+y3=1

c2=1, d2=8e22=1-18=78

 e12+e22=4340,    e1e2=7210,    |e12-e22|=2740

 



Q 16 :

In a triangle ABC with fixed base BC, the vertex A moves such that cosB+cosC=4sin2A2. If a, b and c denote the lengths of the sides of the triangle opposite to the angles A, B and C, respectively, then                   [2009]

  • b+c=4a

     

  • b+c=2a

     

  • locus of point A is an ellipse

     

  • locus of point A is a pair of straight lines

     

Select one or more options

(2, 3)

In ABC,  cosB+cosC=4sin2A2    (Given)

2cosB+C2cosB-C2-4sin2A2=0

2sinA2[cosB-C2-2sinA2]=0

sinA2=0  or  cosB-C2-2cosB+C2=0

Since in a triangle, sinA20

  cosB-C2-2cosB+C2=0 cos(B+C2)cos(B-C2)=12

By componendo and dividendo, we get

cos(B+C2)+cos(B-C2)cos(B+C2)-cos(B-C2)=1+21-2=-3

2cosB2cosC2-2sinB2sinC2=-3tanB2tanC2=13

(s-a)(s-c)s(s-b)(s-a)(s-b)s(s-c)=13

s-as=132s=3aa+b+c=3ab+c=2a

i.e. AC+AB=constant               ( Base BC=a is given to be constant)

 Locus of A is an ellipse.



Q 17 :

Let P(x1,y1) and Q(x2,y2), where y1<0, y2<0, be the end points of the latus rectum of the ellipse x2+4y2=4. The equations of parabolas with latus rectum PQ are                                         [2008]

  • x2+23y=3+3

     

  • x2-23y=3+3

     

  • x2+23y=3-3

     

  • x2-23y=3-3

     

Select one or more options

(2, 3)

Given ellipse is x2+4y2=4

or x222+y21=1a=2, b=1

  e=1-14=32        ae=3

As per question P(ae,-b2a)=(3,-12)

                      Q(-ae,-b2a)=(-3,-12)          PQ=23

Now if PQ is the length of latus rectum of the parabola whose equation is to be found, then

PQ=4a23=4aa=32

Also as PQ is horizontal, parabola with PQ as latus rectum can be upward parabola (with vertex at A) or downward parabola  (with vertex at A') as shown in the figure.

For upward parabola,

AR=a=32,         Coordinates of A=(0,-(3+12))

 Equation of upward parabola is

x2=23(y+3+12)x2-23y=3+3         (i)

For downward parabola        A'R=a=32

  Coordinates of A'=(0,-(1-32))

 Equation of downward parabola is given by

x2=-23(y+1-32)x2+23y=3-3         (ii)

  Equation of required parabola is given by equation (i) or (ii) 



Q 18 :

Consider the ellipse x24+y23=1.

Let H(α,0), 0<α<2, be a point. A straight line drawn through H parallel to the y-axis crosses the ellipse and its auxiliary circle at points E and F respectively, in the first quadrant. The tangent to the ellipse at the point E intersects the positive x-axis at a point G. Suppose the straight line joining F and the origin makes an angle ϕ with the positive x-axis.                               [2022]

  List-I   List-II
(I) If ϕ=π4, then the area of the triangle FGH is (P) (3-1)48
(II) If ϕ=π3, then the area of the triangle FGH is (Q) 1
(III) If ϕ=π6, then the area of the triangle FGH is (R) 34
(IV) If ϕ=π12, then the area of the triangle FGH is (S) 123
    (T) 332

 

The correct option is:

  • (I) → (R); (II) → (S); (III) → (Q); (IV) → (P)

     

  • (I) → (R); (II) → (T); (III) → (S); (IV) → (P)

     

  • (I) → (Q); (II) → (T); (III) → (S); (IV) → (P)

     

  • (I) → (Q); (II) → (S); (III) → (Q); (IV) → (P)

     

(3)

Let F(2cosϕ,2sinϕ) and E(2cosϕ,3sinϕ)

α2cosϕ

Tangent at E(2cosϕ,3sinϕ) to ellipse x24+y23=1

i.e. xcosϕ2+ysinϕ3=1    intersects x-axis at G(2secϕ,0)

Area of triangle FGH=12HG×FH

=12(2secϕ-2cosϕ)2sinϕ;  Δ=2sin2ϕ·tanϕ

Δ=(1-cos2ϕ)·tanϕ

I. If ϕ=π4,  Δ=1(Q)

II. If ϕ=π3,  Δ=2(32)2·3=332(T)

III. If ϕ=π6,  Δ=2(12)2·13=123(S)

IV. If ϕ=π12,  Δ=(1-32)(2-3)=(2-3)22(P)



Q 19 :

Let F1(x1,0) and F2(x2,0), for x1<0 and x2>0, be the foci of the ellipse x29+y28=1. Suppose a parabola having vertex at the origin and focus at F2 intersects the ellipse at point M in the first quadrant and at point N in the fourth quadrant.                          [2016]

Q.     The orthocentre of the triangle F1MN is

  • (-910,0)

     

  • (23,0)

     

  • (910,0)

     

  • (23,6)

     

(1)

Given : Ellipse x29+y28=1

e=1-89=13                  (i)

 F1(-1,0) and F2(1,0)

Parabola with vertex at (0,0) and focus at F2(1,0) is

y2=4x                  (ii)

  On solving (i) and (ii), we get the intersection points of ellipse and parabola as

M(32,6) and N(32,-6)

One altitude of F1MN is x-axis i.e. y=0 and altitude from M to F1N is

y-6=526(x-32)

Putting y=0 in above equation, we get x=-910

  Orthocentre (-910,0)



Q 20 :

Let F1(x1,0) and F2(x2,0), for x1<0 and x2>0, be the foci of the ellipse x29+y28=1. Suppose a parabola having vertex at the origin and focus at F2 intersects the ellipse at point M in the first quadrant and at point N in the fourth quadrant.               [2016]

Q.   If the tangents to the ellipse at M and N meet at R and the normal to the parabola at M meets the x-axis at Q, then the ratio of area of the triangle MQR to area of the quadrilateral MF1NF2 is

  • 3 : 4

     

  • 4 : 5

     

  • 5 : 8

     

  • 2 : 3

     

(3)

Given : Ellipse x29+y28=1

e=1-89=13            (i)

  F1(-1,0) and F2(1,0)

Parabola with vertex at (0,0) and focus at F2(1,0) is

y2=4x               (ii)

   On solving (i) and (ii), we get the intersection points of ellipse and parabola as

         M(32,6) and N(32,-6)

Tangents to ellipse at M and N are

x6+y68=1                  (i)

and    x6-y68=1              (ii)

On solving (i) and (ii), we get their intersection point R(6,0).

Now equation of normal to parabola at M(32,6) is

y-6=-62(x-32)

Its intersection with x-axis is Q(72,0)

Now area (MQR)=12×52×6=564

Now area (MF1NF2)=2×area (F1MF2)=2×12×2×6=26

  area (MQR)area (MF1NF2)=564×26=5:8



Q 21 :

Tangents are drawn from the point P(3, 4) to the ellipse x29+y24=1 touching the ellipse at points A and B.                [2010]

Q.     The coordinates of A and B are

  • (3,0) and (0,2)

     

  • (-85,216115)  and  (-95,85)

     

  • (-85,216115)  and  (0,2)

     

  • (3,0)  and  (-95,85)

     

(4)

Tangent to x232+y222=1 at the point (3cosθ,2sinθ) is

xcosθ3+ysinθ2=1

Since it passes through (3,4),

 cosθ+2sinθ=1

4sin2θ=1+cos2θ-2cosθ

5cos2θ-2cosθ-3=0

cosθ=1,-35sinθ=0,45

 Required points are A(3,0) and B(-95,85)



Q 22 :

Tangents are drawn from the point P(3, 4) to the ellipse x29+y24=1 touching the ellipse at points A and B.               [2010]

Q.   The orthocenter of the triangle PAB is

  • (5,87)

     

  • (75,258)

     

  • (115,85)

     

  • (825,75)

     

(3)

Let H be the orthocentre of PAB, then as BHAP, BH is a horizontal line through B.

  y-coordinate of B=85

Let H has coordinate (α,85).

 Slope of PH=85-4α-3=-125(α-3)

and slope of AB=85-0-95-3=8-24=-13

But PHAB,     -125(α-3)×(-13)=-1

4=-5α+15 or α=115          H(115,85).



Q 23 :

Tangents are drawn from the point P(3, 4) to the ellipse x29+y24=1 touching the ellipse at points A and B.               [2010]

Q.      The equation of the locus of the point whose distances from the point P and the line AB are equal, is

  • 9x2+y2-6xy-54x-62y+241=0

     

  • x2+9y2+6xy-54x+62y-241=0

     

  • 9x2+9y2-6xy-54x-62y-241=0

     

  • x2+y2-2xy+27x+31y-120=0

     

(1)

Clearly the moving point traces a parabola with focus at P(3,4) and directrix as

AB: y-0x-3=-13x+3y-3=0

 Equation of parabola is

(x-3)2+(y-4)2=(x+3y-3)210

9x2+y2-6xy-54x-62y+241=0