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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
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.
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