CBSE Class 12 Math 2013 Solved Paper
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Question : 21 of 29
Marks:
+1,
-0
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 = 0 and = 0 and which is perpendicular to the plane = 0
OR
Find the vector equation of the plane which contains the line of intersection of the planes = 0 and = 0 and which is perpendicular to the plane = 0
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 =
Thus, the angle between the given line and the given plane is
OR
The equation of the given planes are
= 0 ... (1)
= 0 ... (2)
The equation of the plane passing through the intersection of the planes (1) and (2) is
+ λ = 4 - 5λ ... (3)
Given that plane (3) is perpendicular to the plane = 0
1 + 2λ × 5 + 2 + λ × 3 + 3 - λ × - 6 = 0
⇒ 19λ - 7 = 0
⇒ λ =
Putting λ = in (3), we get
= 4 -
⇒ =
⇒ = 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
= 0 ... (1)
= 0 ... (2)
The equation of the plane passing through the intersection of the planes (1) and (2) is
+ λ = 4 - 5λ ... (3)
Given that plane (3) is perpendicular to the plane = 0
1 + 2λ × 5 + 2 + λ × 3 + 3 - λ × - 6 = 0
⇒ 19λ - 7 = 0
⇒ λ =
Putting λ = in (3), we get
⇒ =
⇒ = 41. This is the equation of the required plane.
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