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12th Grade > Mathematics

ELLIPSE AND HYPERBOLA MCQs

Total Questions : 30 | Page 2 of 3 pages
Question 11. If the ellipse x2a23+y2a+4=1 is inscribed in a square of side length a2 then a is
  1.    4
  2.    2
  3.    1
  4.    None of these
 Discuss Question
Answer: Option D. -> None of these
:
D
Sides of the square will be perpendicular tangents to the ellipse so, vertices of the square will lie on director circle. So diameter of director circle is
2(a23)+(a+4)=2a2+2a22a2+a+1=2aa=1Butforellipsea2>3&a>4
So there is no value of a which satisfy both.
Question 12. Tangents are drawn from any point on the circle x2+y2=41 to the Ellipse x225+y216=1 then the angle between the two tangents is
  1.    π4
  2.    π3
  3.    π6
  4.    π2
 Discuss Question
Answer: Option D. -> π2
:
D
The given circle is the director circle of the ellipse,so the angle between the tangents is π2.
Question 13. The perimeter of a triangle is 20 and the points (-2, -3) and (-2, 3) are two of the vertices of it. Then the locus of third vertex is :
  1.    (x−2)249+y240=1
  2.    (x+2)249+y240=1
  3.    (x+2)240+y249=1
  4.    (x−2)240+y249=1
 Discuss Question
Answer: Option C. -> (x+2)240+y249=1
:
C
A(2,3),B(2,3)
Let the third vertex be C(x,y)
AB + BC+CA=20
BC+CA=14
So locus of C is ellipse with A,B as focii.
2a=14
2ae=6
e=37
we get b as 40
Equation of ellipse is (x+2)240+y249=1
Question 14. The equation of a hyperbola, conjugate to the hyperbola x2+3xy+2y2+2x+3y+1=0, is
  1.     x2+3xy+2y2+2x+3y+1=0
  2.    x2+3xy+2y2+2x+3y+2=0
  3.     x2+3xy+2y2+2x+3y+3=0
  4.    x2+3xy+2y2+2x+3y+4=0
 Discuss Question
Answer: Option B. -> x2+3xy+2y2+2x+3y+2=0
:
B
We know that,
Equation of hyperbola + Equation of conjugate
hyperbola = 2(Equation of asymptotes)
Equation of conjugate hyperbola
= 2 Equation of asymptotes - Equation of hyperbola
C(x, y) = 2A(x, y) – H(x, y) …… (i)
H(x,y)x2+3xy+2y2+2x+3y=0
Equation of asymptotes is
x2+3xy+2y2+2x+3y+λ=0
Δ=0,abc+2fghaf2bg2ch2=0,thenλ=1
A(x,y)x2+3xy+2y2+2x+3y+1=0
C(x,y)x2+3xy+2y2+2x+3y+2=0[from equation (i)]
Question 15. If two tangents can be drawn to the different branches of hyperbola
x21y24=1 from the paint (α,α2),        then 
  1.    αϵ(−2,0)  
  2.    αϵ(−3,0)
  3.    αϵ(−∞,−2)  
  4.    αϵ(−∞,−3)
 Discuss Question
Answer: Option C. -> αϵ(−∞,−2)  
:
C
Given that,
x21y24=1
If Two Tangents Can Be Drawn To The Different Branches Of Hy...
Since, (α,α2) lie on the parabola y=x2, then (α,α2) must lie between the asymptotes of hyperbola x21y24=1 in 1st and 2nd quadrants.
So, the asymptotes are y=±2x
2α<α2
α<0orα>2 and 2α<α2
α<2or2α<0
αϵ(,2)or(2,)
Question 16. The eccentricity of the rectangular hyperbola is
  1.    2
  2.    √2
  3.    0
  4.    None of these
 Discuss Question
Answer: Option B. -> √2
:
B
In case of rectangular hyperbola,
a=bb2=a2a2(e21)=a2e=2
Question 17. A man running round a race course notes that the sum of the distances of two flag posts from him is 8 meters.The area of the path he encloses in square meters if the distance between flag posts is 4 is
  1.    15√3π
  2.    12√3π
  3.    18√3π
  4.    8√3π
 Discuss Question
Answer: Option D. -> 8√3π
:
D
The path he runs is an ellipse whose major axis is 4m,e=12
Area=π ab
Question 18. If a variable tangent of the circle x2+y2=1 intersect the ellipse x2+2y2=4 at P and Q then the locus of the points of intersection of the tangents at P and Q is
  1.      A circle of radius 2 units
  2.      A parabola with fouc as (2, 3)
  3.    An ellipse with eccentricity √34
  4.    An ellipse with length of latus rectrum is 2 units
 Discuss Question
Answer: Option D. -> An ellipse with length of latus rectrum is 2 units
:
D
x2+y2=1; x2+2y2=4
Let R(x1,y1) is point of intersection of tangents drawn at P,Q to ellipse PQ is chord of contact of R(x1,y1)
xx1+2yy14=0
This touches circle r2(l2+m2)=n21(x21+4y21)=16x2+4y2=16isellipsewitheccentricitye=32andlengthoflatusrectumLL1=2
Question 19. The product of the perpendicular from any point on the hyperbola x2a2y2b2=1 to its asymptotes, is equal to
 
  1.    aba+b
  2.    a2b2a2+b2
  3.    2a2b2a2+b2
  4.    None of these
 Discuss Question
Answer: Option B. -> a2b2a2+b2
:
B
Let (asecθ,btanθ) be the any point on the hyperbola x2a2y2b2=1
The equations of the asymptotes of the given hyperbola are xayb=0 and xa+yb=0
Now, p1 = length of the perpendicular from (asecθ,btanθ) on xa+yb=0
=secθtanθ1a2+1b2
and p2 = length of the perpendicular from (asecθ,btanθ) xa+yb=0
=secθtanθ1a2+1b2
p1p2=sec2θtan2θ1a2+1b2=a2b2a2+b2
Question 20. The locus of the middle points of chords of hyperbola 3x22y2+4x6y=0  parallel to y = 2x, is
 
  1.    3x – 4y = 4
  2.    3y – 4x + 4 = 0
  3.    4x – 4y = 3
  4.    3x – 4y = 2
 Discuss Question
Answer: Option A. -> 3x – 4y = 4
:
A
By T = S1, the equation of chord whose mid-point is (α,β) is 3xα2yβ+(x+α)2(y+β)=0
x(3α+2)y(2β+3)=2
as it is parallel to y = 2x
3α4β=4
Required locus is 3x – 4y = 4

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