The distance of the line from the point along the line is:
- A
- B
- C
- D
The distance of the line from the point along the line is:
Correct answer:B
Standard Method
Given: The line is , the point is , and the distance is to be measured along the line .
Find: The required distance.
Take the direction ratios of the second line as . A plane perpendicular to this line and passing through has normal vector .
So the equation of the plane is
which simplifies to
For the first line , a point on it is .
Substitute into the plane:
Hence the distance from the line to the plane is
Therefore, the distance of the line from the point along the given line is . The correct option is B.
Vector Form Method
Given: The first line in symmetric form is and the second line is .
Find: The distance from point to the first line measured along the given direction.
Write the first line in parametric form:
So its direction vector is .
The second line has direction vector .
Using the approach stated in the solution, the required distance comes out to be after evaluating the corresponding vector relation. Hence, the correct option is B.
Using the direction ratios of the first line, , as the normal to the plane. This is wrong because the distance is measured along the second line, so the plane must be perpendicular to the second line. Use normal vector instead.
Applying the point-to-line distance formula directly without noticing the phrase 'along the line'. This is wrong because the question asks for directional distance, which is handled here by constructing a plane perpendicular to the given line of direction .
Substituting the point into the plane incorrectly. This gives a wrong numerator in the distance formula. Compute carefully before dividing by .
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