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Question : 21
Total: 29
Find the angle between the following pair of lines:
=
=
and
=
=
And check whether the lines are parallel or perpendicular.
And check whether the lines are parallel or perpendicular.
Solution:
Let
and
be the vector parallel to the pair to lines,
=
=
and
=
=
, respectively.
Now,
=
=
⇒
=
=
=
=
⇒
=
=
∴
= 2
+ 7
− 3
and
= −
+ 2
+ 4
|
| = √ ( 2 ) 2 + ( 7 ) 2 + ( − 3 ) 2 = √ 62
|
| = √ ( − 1 ) 2 + ( 2 ) 2 + ( 4 ) 2 = √ 21
.
= ( 2
+ 7
− 3
) . ( −
+ 2
+ 4
)
= 2 (- 1) + 7 × 2 + (- 3) . 4
= - 2 + 14 - 12
= 0
The angle θ between the given pair of lines is given by the relation,
cos θ =|
|
⇒ cos θ =
= 0
⇒ θ =c o s − 1 (0) =
Thus, the given lines are perpendicular to each other and the angle between them is 90°.
Now,
⇒
∴
= 2 (- 1) + 7 × 2 + (- 3) . 4
= - 2 + 14 - 12
= 0
The angle θ between the given pair of lines is given by the relation,
cos θ =
⇒ cos θ =
⇒ θ =
Thus, the given lines are perpendicular to each other and the angle between them is 90°.
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