Page 74 - Mathematics Class - XI

Viva-Voce

1. What do you understand by the conic section?
Ans. A conic section is a curve obtained as the intersection of a cone with a plane. The four types of conic
sections are hyperbola, parabola, ellipse and circle.
2. How do the circular disc and parabolic disc reflect back the light?
Ans. ● Circular disc reflects back the light issuing from centre to the centre again.
● Parabolic disc reflects back the light issuing from one focus to the other focus.
3. State the relationship between slant height, radius and height of a cone.

Ans. l = h + r , where l = slant height, h = height and r = radius
2
2
2
4. State the equation of the hyperbola in standard form.
x 2 y 2
Ans. The equation of the hyperbola in standard form is − = 1.
a 2 b 2
5. Define hyperbola.
Ans. A hyperbola is the set of all points in a plane, the difference of whose distances from two fixed points in
the plane is a constant.
6. An equation is given to you, by seeing that equation how can you identified whether that will be a circle
or not?
Ans. Condition of circle is
Coefficient of x = Coefficient of y 2
2
7. If the equation of circle, x + y + 2gx + 2fy + c = 0 is given then what will be its centre coordinates and its
2
2
radius?
Ans. Coordinate of centre ⇒ (– g, – f )

radius = g f c
2
2

MCQs

1. If eccentricity (e) = 0, then what will be the shape of this conic section?

a) parabola b) circle c) hyperbola d) ellipse
2. In case of parabola, the value of eccentricity (e) is
a) e = 0 b) e = 1 c) e > 1 d) e < 1

3. The area of circle which is passing through the point (3, 6) and its centre is at (1, 2).
a) 10 p b) 25 p c) 5 p d) 15 p
4. The centre of the circle x + y – 10 x – 6 y = 0
2
2
a) (5, 10) b) (5, 3) c) (0, 0) d) (0, 3)

Answers: 1. b) circle 2. b) e = 1 3. b) 25 p 4. b) (5, 3)

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