Animated Solution for Mathematics - Three Dimensional Geometry: The distance of the point (1,−2,3) from the plane x−y+z=5 measured parallel to the line 2x=3y=−6z is:
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Visualized Solution
Visualizing the Geometry
Given Point: P(1,−2,3)
Target Plane: x−y+z=5
Goal: Find the distance from P to the plane, but not the perpendicular distance.
Identifying the Direction
The measurement must be parallel to the line: 2x=3y=−6z
The Direction Ratios (DRs) of this line are (2,3,−6).
Our path from P will share these exact direction ratios.
Equation of the Line through P
Line passes through P(1,−2,3).
Direction Ratios: (2,3,−6).
Equation of the line: 2x−1=3y+2=−6z−3=λ
General Point on the Line
Expressing coordinates in terms of λ:
x=2λ+1
y=3λ−2
z=−6λ+3
General point Q=(2λ+1,3λ−2,−6λ+3)
Intersection with the Plane
Point Q must lie on the plane x−y+z=5.
Substitute Q's coordinates into the plane's equation:
Key Concept: Distance measured parallel to a line requires finding the intersection point of the line and the plane.
JEE Trap: Never use the perpendicular distance formula d=a2+b2+c2∣ax1+by1+cz1−d∣ when a specific direction is given!
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The Sigma Insight: Intersection of a Line and a Plane
Solution Diagram
Analyzing the Setup
We are given a point P(1,−2,3) and a plane defined by the equation:
x−y+z=5
We are tasked with finding the distance from point P to this plane, measured along the direction of the line defined by the vector v=2i^+3j^−6k^.
The Parametric Path
To find the intersection point Q where the trajectory meets the plane, we express the line passing through P in parametric form. Using the direction ratios (2,3,−6) and the starting point (1,−2,3), any point Q on this line can be represented as:
x=2λ+1
y=3λ−2
z=−6λ+3
Here, λ represents the scalar parameter that allows us to traverse the line.
Finding the Intersection
To find the specific point Q that lies on the plane, we substitute these parametric coordinates into the plane equation x−y+z=5:
(2λ+1)−(3λ−2)+(−6λ+3)=5
Simplifying the expression:
2λ+1−3λ+2−6λ+3=5
−7λ+6=5
−7λ=−1
Solving for the parameter, we find:
λ=71
Final Calculation
Now that we have λ=71, we can determine the distance PQ. The distance between point P and point Q is given by the magnitude of the vector PQ=λv.
The distance d is:
d=∣λ∣⋅∣v∣
First, calculate the magnitude of the direction vector v=2i^+3j^−6k^:
∣v∣=22+32+(−6)2=4+9+36=49=7
Substituting the values of λ and ∣v∣:
d=71⋅7=1
The distance from point P to the plane along the given direction is 1.