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Question : 21
Total: 29
Find the coordinates of the point, where the line
=
=
intersects the plane x – y + z – 5 = 0. Also find the angle between the line and the plane.
OR
Find the vector equation of the plane which contains the line of intersection of the planes
.
+ 2
+ 3
− 4 = 0 and
.2
+
−
+ 5 = 0 and which is perpendicular to the plane
.5
+ 3
− 6
+ 8 = 0
OR
Find the vector equation of the plane which contains the line of intersection of the planes
Solution:
The equation of the given line is
=
=
... (1)
Any point on the given line is (3λ + 2, 4λ - 1 , 2λ + 2)
If this point lies on the given plane x – y + z – 5 = 0, then
3λ + 2 -(4λ - 1) + 2λ + 2 - 5 = 0
⇒ λ = 0
Putting λ = 0 in (3λ + 2, 4λ - 1 , 2λ + 2) , we get the point of intersection of the given line and the plane is (2, -1, 2).
Let θ be the angle between the given line and the plane
∴ sin θ =
=
=
=
⇒ θ =s i n − 1 (
)
Thus, the angle between the given line and the given plane iss i n − 1 (
)
OR
The equation of the given planes are
.
+ 2
+ 3
− 4 = 0 ... (1)
.2
+
−
+ 5 = 0 ... (2)
The equation of the plane passing through the intersection of the planes (1) and (2) is
|
.
+ 2
+ 3
− 4 | + λ |
.2
+
−
+ 5 | = 4 - 5λ ... (3)
Given that plane (3) is perpendicular to the plane
.5
+ 3
− 6
+ 8 = 0
1 + 2λ × 5 + 2 + λ × 3 + 3 - λ × - 6 = 0
⇒ 19λ - 7 = 0
⇒ λ =
Putting λ =
in (3), we get
| ( 1 +
)
+ ( 2 +
)
+ ( 3 −
)
| = 4 -
⇒
. (
+
+
) =
⇒
.33
+ 45
+ 50
= 41. This is the equation of the required plane.
Any point on the given line is (3λ + 2, 4λ - 1 , 2λ + 2)
If this point lies on the given plane x – y + z – 5 = 0, then
3λ + 2 -(4λ - 1) + 2λ + 2 - 5 = 0
⇒ λ = 0
Putting λ = 0 in (3λ + 2, 4λ - 1 , 2λ + 2) , we get the point of intersection of the given line and the plane is (2, -1, 2).
Let θ be the angle between the given line and the plane
∴ sin θ =
⇒ θ =
Thus, the angle between the given line and the given plane is
OR
The equation of the given planes are
The equation of the plane passing through the intersection of the planes (1) and (2) is
Given that plane (3) is perpendicular to the plane
1 + 2λ × 5 + 2 + λ × 3 + 3 - λ × - 6 = 0
⇒ 19λ - 7 = 0
⇒ λ =
Putting λ =
⇒
⇒
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