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A line with positive direction cosines passes through the point P(2, –1, 2) and makes equal angles with the coordinate axes. The line meets the plane 2x + y + z = 9 at point Q. The length of the line segment PQ equals
  • a)
    1
  • b)
    √2
  • c)
    √3
  • d)
    2
Correct answer is option 'C'. Can you explain this answer?
Verified Answer
A line with positive direction cosines passes through the point P(2, &...
The line has +ve and equal direction cosines, these are   or direction ratios are 1, 1, 1. Also thelines passes through P (2, – 1, 2).
∴ Equation  of line is
 be a point on this line where it meets the plane 2 x + y + z = 9
Then Q must satisfy the eqn of plane
∴ Q has coordintes (3, 0, 3)
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Most Upvoted Answer
A line with positive direction cosines passes through the point P(2, &...
Given Information:
Point P(2, -1, 2)
Line with positive direction cosines passing through P
Line makes equal angles with coordinate axes
Plane 2x + y + z = 9
Point of intersection with plane is Q

Solution:

Step 1: Finding Direction Ratios of the Line
Since the line makes equal angles with the coordinate axes, the direction cosines will be equal.
Let the direction cosines be (l, l, l), where l is a constant.
Since the line passes through point P(2, -1, 2), we can write:
2/l = -1/l = 2/l
This gives us l = ±√3

Step 2: Finding Point Q
The line intersects the plane at point Q, so the coordinates of Q satisfy the equation of the plane:
2x + y + z = 9
Substitute the coordinates of Q as (2√3t, -√3t, 2√3t) where t is a parameter.
Plug these values into the equation of the plane and solve for t:
2(2√3t) + (-√3t) + 2√3t = 9
4√3t - √3t + 2√3t = 9
5√3t = 9
t = 9/(5√3) = √3/5

Step 3: Calculating Length of PQ
The coordinates of Q are (2√3(√3/5), -√3(√3/5), 2√3(√3/5)) = (6/5, -3/5, 6/5)
Using the distance formula, the length of PQ = √[(6-2)^2 + (-3+1)^2 + (6-2)^2] = √(16 + 4 + 16) = √36 = √3
Therefore, the length of the line segment PQ is √3, which corresponds to option 'c'.
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A line with positive direction cosines passes through the point P(2, –1, 2) and makes equal angles with the coordinate axes. The line meets the plane2x + y + z = 9at point Q. The length of the line segment PQ equalsa)1b)√2c)√3d)2Correct answer is option 'C'. Can you explain this answer?
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