Page 87 - Mathematics Class - XI

Viva-Voce

1. If a point is in YZ plane, then what is its x-coordinates?
Ans. In YZ plane, x-coordinates of point is zero.

2. What is an octant?
Ans. Coordinates plane divides the space into 8 parts and each part is called an octant.
3. Identify the octant in which the following point lies.

(a) (–5, –8, 1) (b) (1, –2, 4)
Ans. (a) III octant (b) IV octant

4. What is the distance of a point P (4, –3, 1) from the origin O?

Ans. |OP| = (04 ) (03 ) (01 ) 16 91 = 5.09 units.
2
2
2
5. Which octant has all positive coordinates?
Ans. Octant OXYZ has all positive coordinates.
6. What are the coordinates of the mid-point of the line segment joining two points P ( x , y , z ) and
1
1
1
Q ( x , y , z )?
2
2
2
Ans. Coordinates of the mid-points are x x 2 , y y 2 , z z .

1
2

1
1
2 2 2
MCQs

1. The perpendicular point on the x-axis from the point P (3, 4, 5) is
a) (3, 4, 0) b) (0, 4, 5) c) (3, 0, 5) d) (3, 0, 0)

2. The octant of the point (–2, 3, –3) is
a) I b) II c) III d) None of these

3. The perpendicular distance from point P (a, b, c) to z-axis.
a) a + b 2 b) b + c 2 c) a + c 2 d) a + 2 b + 2 c 2
2
2
2
4. The points A (5, –4, 2), B (4, –3, 1), C (7, 6, 4) and D (8, –7, 5) are the vertices of a
a) rectangle b) square c) Parallelogram d) None of these
5. A point for which the locus of y = 0, z = 0 is
a) equation of x-axis b) equation of y-axis c) equation of z-axis d) none of these

6. The point (0, 6, –4) is located in which plane
a) xy plane b) yz plane c) zx plane d) none of these

Answers: 1. d) (3, 0, 0) 2. d) None of these 3. a) a + b 2
2
4. a) rectangle 5. a) equation of x-axis 6. b) yz plane
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