

NCERT Solutions for Class 12 Maths Chapter 10 Miscellaneous Exercise
Solution :
The given vectors are:
Question
2. Write two different vectors having same magnitude.
Solution :
Hence, and are two different vectors having the same magnitude. The vectors are different because they have different directions.
NCERT Solutions for Class 12 Maths Chapter 10 Exercise 10.1
Question 3. Write two different vectors having same direction. Solution :
The direction cosines of and are the same. Hence, the two vectors have the same direction.
NCERT Solutions for Class 12 Maths Chapter 10 Exercise 10.3
Question4
.
Find the values of
x
and
y
so that the vectors
are equal
will be equal if their corresponding components are equal.
Hence, the required values of
x
and
y
are 2 and 3 respectively.
Question
5. Find the scalar and vector components of the vector with initial point (2, 1) and terminal point (–5, 7).
Solution :
The vector with the initial point P (2, 1) and terminal point Q (–5, 7) can be given by,
Hence, the required scalar components are –7 and 6 while the vector components are
Question
6. Find the sum of the vectors:
Solution :
Given:
Question
7. Find the unit vector in the direction of the vector
Solution :
The unit vector in the direction of vector
is given by = / |a|
Question
8. Find the unit vector in the direction of the vector
where P and Q are the points (1, 2, 3) and (4, 5, 6) respectively.
Solution :
Given: Points P (1, 2, 3) and Q (4, 5, 6)
Hence, the unit vector in the direction of
is
Question
9. For given vectors
find the unit vector in the direction of +
Solution :
Given: Vectors
Hence, the unit vector in the direction of (
+ )
is
Question
10. Find the vector in the direction of vector which has magnitude 8 units.
Solution :
Let
=
Hence, the vector in the direction of vector
which has magnitude 8 units is given by,
Question
11. Show that the vectors are collinear.
Solution :
Let
= λ
where λ = 2
Hence, the given vectors are collinear.
Question
12. Find the direction cosines of the vector
Solution :
The given vector is =
We know that the direction cosines of a vector
are coefficients of
Question
13. Find the direction cosines of the vector joining the points A (1, 2, –3) and
B (–1, –2, 1) directed from A to B.
Solution :
The given points are A (1, 2, –3) and B (–1, –2, 1).
Question
14. Show that the vector
is equally inclined to the axes OX, OY and OZ.
Solution :
Let =
Hence, the given vector is equally inclined to axes OX, OY, and OZ.
Question
15. Find the position vector of a point R which divides the line joining two points P and Q whose position vectors are
and -
respectively, in the ratio 2 : 1
(i) internally
(ii) externally.
Solution :
The position vector of point R dividing the line segment joining two points
P and Q in the ratio
m:
n
is given by
(i) Internally:
=
(ii) Externally:
=
Position vectors of P and Q are given as:
Question
16. Find the position vector of the mid-point of the vector joining the points P (2, 3, 4) and Q
(4, 1, – 2).
Solution :
The position vector of mid-point R of the vector joining points P (2, 3, 4) and Q (4, 1, – 2) is given by,
Question
17. Show that the points A, B and C with position vectors
respectively form the vertices of a right angled triangle.
Solution :
Position vectors of points A, B, and C are respectively given as:
Hence, ABC is a right-angled triangle.
Question
18. In triangle ABC (Fig. below), which of the following is not true:
Solution :
Hence, the equation given in alternative C is
incorrect
.
The correct answer is
C.
Question
19. If
and
are two collinear vectors, then which of the following are incorrect:
(A)
= λ
for some scalar λ
(B) = ±
(C) The respective components of
and
are proportional.
(D) Both the vectors
and
have same direction, but different magnitudes.
Solution :
Option (D) is not true because two collinear vectors can have different directions and also different magnitudes.
The option (A) and option (C) are true by definition of collinear vectors.
Option (B) is a particular case of option (A).
