Q 11 :

Let m1 and m2 be the slopes of the tangents drawn from the point P(4, 1) to the hyperbola H: y225-x216=1. If Q is the point from which the tangents drawn to H have slopes |m1| and |m2| and they make positive intercepts α and β on the x-axis, then (PQ)2αβ is equal to _________ .        [2023]



(8)

Equation of tangent to the hyperbola y225-x216=1

y=mx±25-16m2                                    ...(i)

Equation (i) passes through (4,1),

1=4m±25-16m2⇒1-4m=±25-16m2

⇒1+16m2-8m=25-16m2⇒32m2-8m-24=0

⇒4m2-m-3=0⇒4m2-4m+3m-3=0

⇒4m(m-1)+3(m-1)=0

⇒(4m+3)(m-1)=0⇒m=1,-34

It is given that |m1| and |m2| are the slopes of tangents, so

|m1|=1 and |m2|=34

Equations of tangents with positive slope are:

y=x±25-16 ⇒y=x±3

and y=34x±25-16×916⇒4y=3x±16

For positive intercept on the x-axis, y=x-3 and 4y=3x-16

∴  α=163 and β=3

Solve y=x-3 and 4y=3x-16 to find their intersection point.

⇒ x=-4 and y=-7

So, Q≡(-4,-7)

(PQ)2=(4+4)2+(1+7)2=64+64=128

∴  (PQ)2αβ=12816=8



Q 12 :

The foci of a hyperbola are (±2,0) and its eccentricity is 32. A tangent perpendicular to the line 2x+3y=6 is drawn at a point in the first quadrant on the hyperbola. If the intercepts made by the tangent on the x- and y-axes are a and b respectively, then |6a|+|5b| is equal to _________ .        [2023]



(12)

e=32, ae=2

⇒a=43⇒e2=1+b2a2

⇒54=9b216⇒b2=54×169=209

Equation of tangent:  y=mx+a2m2-b2

y=32x+169·94-209

y=32x+43

y-intercept=43,  x-intercept=-89

|6a|+|5b|=|6×-89|+|5×43|=163+203=363=12



Q 13 :

The vertices of a hyperbola H are (±6,0) and its eccentricity is 52. Let N be the normal to H at a point in the first quadrant and parallel to the line 2 x+y=22. If d is the length of the line segment of N between H and the y-axis, then d2 is equal to _________ .        [2023]



(216)

Equation of hyperbola =x236-y2b2=1

Let H be (x1,y1)

b2=36(54-1)=9

Hyperbola: x236-y29=1

Equation of normal: 36xx1+9yy1=45⇒-4y1x1=-2

x1=22 y1 and (22 y1)236-y129=1

8y1236-y129=1⇒y1=3(y1>0)⇒x1=62

Equation of normal: y=-2 x+15

This intersects the y–axis at (0,15)

d2 =(62-0)2+(3-15)2

=72+144=216



Q 14 :

Let the domain of the function f(x)=log3log5log7(9x-x2-13) be the interval (m,n). Let the hyperbola x2a2-y2b2=1 have eccentricity n3 and the length of the latus rectum 8m3. Then b2-a2 is equal to:             [2026]

  • 9

     

  • 11

     

  • 5

     

  • 7

     

(4)

log5(log7(9x-x2-13))>0

⇒  9x-x2-13>7

        x2-9x+20<0⇒4<x<5

        m=4, n=5

⇒  e=1+b2a2=53⇒b2a2=259-1=169

       ba=43

⇒  2b2a=8m3⇒2b2a=323

⇒  2b2=323×3b4⇒b=4, a=3

        b2-a2=16-9=7



Q 15 :

Let the foci of a hyperbola coincide with the foci of the ellipse x236+y216=1. If the eccentricity of the hyperbola is 5 then the length of its latus rectum is:  [2026]

  • 245

     

  • 965

     

  • 12

     

  • 16

     

(2)

Let e1 be eccentricity of ellipse

⇒e1=1-1636=1-49=53

So ae1=6·53=25

Now H:x2p2-y2q2=1

p.e=ae1

p·5=25

p=25⇒e2=1+q2p2⇒25=1+5q24⇒q2=965

So length of LR=2q2p=965



Q 16 :

If the line αx+2y=1, where α∈ℝ, does not meet the hyperbola x2-9y2=9, then a possible value of α is:       [2026]

  • 0.5

     

  • 0.6

     

  • 0.7

     

  • 0.8

     

(4)

y=1-αx2

Put this in equation of hyperbola

∴ x2-9(1-αx2)2=9

(4-9α2)x2+18αx-45=0

∵  line does not intersect hyperbola

∴ D<0

⇒α2-59>0

⇒α∈(-∞,-53)∪(53,∞)

Here 53≈0.74



Q 17 :

Let the ellipse E:x2144+y2169=1 and the hyperbola H:x216-y2λ2=-1 have the same foci. If e and L respectively denote the eccentricity and the length of latus rectum of H, then the value of 24(e+L) is :   [2026]

  • 148

     

  • 126

     

  • 296

     

  • 67

     

(3)

Equation of hyperbola: y2λ2-x216=1

Equation of ellipse: x2144+y2169=1

e=1-144169=513

Focus⇒(0,5)

⇒λ1+16λ2=5

⇒λ2+16=25⇒λ=3

Eccentricity of hyperbola =1+16λ2=53

Length of latus rectum of hyperbola =2(16)3=323

24(e+ℓ)=24(53+323)=8×37=296



Q 18 :

Let PQ be a chord of the hyperbola x24-y2b2=1 perpendicular to the x-axis such that OPQ is an equilateral triangle, O being the centre of the hyperbola. If the eccentricity of the hyperbola is 3 then the area of the triangle OPQ is.   [2026]

  • 95

     

  • 835

     

  • 115

     

  • 23

     

(2)

e=1+b4=3 ⇒ b=8

∴ Hyperbola:   x24-y28=1

PMOM=tan30°

⇒22tanθ2secθ=13 ⇒ sinθ=16

Area=2×12×OM×MP

=2secθ×22tanθ

=42 sinθcos2θ

=42×16(1-16)

=835



Q 19 :

Let P(10, 215) be a point on the hyperbola x2a2-y2b2=1, whose foci are S and S'. If the length of its latus rectum is 8 then the square of the area of ∆PSS' is equal to: [2026]

  • 4200

     

  • 900

     

  • 1462

     

  • 2700

     

(4)

P(10,215) lies on x2a2-y2b2=1

∴ 100a2-60b2=1    ...(1)

∵   length of latus rectum =8

2b2a=8⇒b2a=4    ...(2)

From (1) & (2)

100a2-604a=1

400-60a=4a2

4a2+60a-400=0

a2+15a-100=0

a=5 & -20 (rejected)

⇒b=20

∴  Hyperbola is x225-y220=1

∴  Focal length S1S2=2ae=2·5(1+45)=65

∴ Area of ∆PS1S2=12·65·215=303=A

∴ A2=2700



Q 20 :

For some θ∈(0,π2), let the eccentricity and the length of the latus rectum of the hyperbola x2-y2sec2θ=8 be e1 and l1, respectively, and let the eccentricity and the length of the latus rectum of the ellipse x2sec2θ+y2=6 be e2 and l2, respectively. If e12=e22(sec2θ+1), then (l1l2e1e2)tan2θ is equal to______. [2026]



(8)

x28-y28cos2θ=1,   e1=1+8cos2θ8

ℓ1=2b2a=2(8cos2θ)22

x26+y26cos2θ=1,   e2=1-6cos2θ6=sinθ

ℓ2=2b2a=2·6cos2θ6

e12=e22(1+sec2θ)

1+cos2θ=sin2θ(1+1cos2θ)

1+cos2θ=sin2θ+tan2θ

Solving we get θ=π4

ℓ1=22

e1=32

ℓ2=6

e2=12

(ℓ1ℓ2e1e2)tan2θ=8  (By putting values)



Q 21 :

Let e be the eccentricity of a hyperbola and f(e) be the eccentricity of its conjugate hyperbola, then ∫(f(e)+f(f(e)))de=g(e) and g(2)=2, then g(e)=

  • 12e2-1+e22

     

  • 12e2+1+e22

     

  • e2-1+e22

     

  • e2+1+e22

     

(3)

Let eccentricity of conjugate hyperbola be e'

∴ 1e2+1e'2=1⇒1e'2=1-1e2⇒e'=ee2-1

∴  f(e)=ee2-1

and f(f(e))=f(e)f2(e)-1=ee2-1e2e2-1-1=e

∴ Given integral=∫(ee2-1+e)de=(e2-1+e22)

g(e)=e2-1+e22+C

g(2)=1+1+C⇒C=0

g(e)=e2-1+e22



Q 22 :

A variable chord of the hyperbola x24-y28=1 subtends a right angle at the centre of the hyperbola. If this chord touches a fixed circle which is concentric with the hyperbola and r is radius of the circle, then r2 is



(8)

Let the variable chord be xcosα+ysinα=p which intersect the hyperbola in A and B.

The joint equation of OA and OB is x24-y28=(xcosα+ysinαp)2

⇒(14-cos2αp2)x2-(18+sin2αp2)y2-(2sinαcosαp2)xy=0

⇒14-cos2αp2-18-sin2αp2=0⇒p2=8

The variable line touches the fixed circle, thus perpendicular distance of (0,0)=Radius

r=|0+0-pcos2α+sin2α|

   ⇒r=|p|=8

∴ equation of the circle is x2+y2=8



Q 23 :

Which of the following is/are true

Statement I: A variable circle cuts two fixed perpendicular lines so that each intercept is of different length, then locus of the centre of the circle is hyperbola.

Statement II: If the eccentric angles of the extremities of a focal chord of a Hyperbola x2a2-y2b2=1 are θ1 and θ2, then eccentricity of the Hyperbola e=cos(θ1+θ22)cos(θ1-θ22)=sin(θ1+θ2)sinθ1+sinθ2

  • Only Statement I is true

     

  • Only Statement II is true

     

  • Both Statement I and II are True

     

  • Both Statement I and II are false

     

(3)

Refer to properties of conics



Q 24 :

Let the director circle of the hyperbola H:x2a2-y2b2=1  (a>b) be denoted by C1 and let director circle of ellipse E:x2a2+y2b2=13  (a>b) be denoted by C2 and C2 is also the director circle of C1 and let e1 and e2 be the eccentricities of the ellipse E and hyperbola H respectively. Then e22e12 is equal to

  • 18

     

  • 12

     

  • 6

     

  • 24

     

(3)

Ortho-centres of triangles formed by three tangents and corresponding normal to a parabola are equidistant from axis of parabola.



Q 25 :

If a hyperbola has length of its conjugate axis is equal to 5 and distance between foci is 13. Then eccentricity of the hyperbola is _____

  • 1312

     

  • 2

     

  • 136

     

  • 138

     

(1)

2b=5,  2ae=13,  4b2=25,  4(a2e2-a2)=25