Math Problem Statement

Find the equation of the plane in coordinate form and determine the intersection point between the plane E and the line g.

Solution

The problem consists of two parts regarding the plane EE and the line gg:

Given Plane EE:

E:x=(123)+r(024)+s(111),r,sRE: \vec{x} = \begin{pmatrix} 1 \\ -2 \\ 3 \end{pmatrix} + r \cdot \begin{pmatrix} 0 \\ 2 \\ -4 \end{pmatrix} + s \cdot \begin{pmatrix} 1 \\ 1 \\ 1 \end{pmatrix}, \quad r, s \in \mathbb{R}

1. Equation of the Plane EE in Coordinate Form:

We are asked to derive the plane's equation in the form Ax1+Bx2+Cx3=DAx_1 + Bx_2 + Cx_3 = D.

We know that the normal vector n\vec{n} to the plane is obtained by taking the cross product of the direction vectors: v1=(024),v2=(111)\vec{v_1} = \begin{pmatrix} 0 \\ 2 \\ -4 \end{pmatrix}, \quad \vec{v_2} = \begin{pmatrix} 1 \\ 1 \\ 1 \end{pmatrix}

Perform the cross product n=v1×v2\vec{n} = \vec{v_1} \times \vec{v_2}: n=i^j^k^024111=i^(2(4))j^(0(4))+k^(02)\vec{n} = \begin{vmatrix} \hat{i} & \hat{j} & \hat{k} \\ 0 & 2 & -4 \\ 1 & 1 & 1 \end{vmatrix} = \hat{i}(2 - (-4)) - \hat{j}(0 - (-4)) + \hat{k}(0 - 2) n=6i^4j^2k^=(642)\vec{n} = 6\hat{i} - 4\hat{j} - 2\hat{k} = \begin{pmatrix} 6 \\ -4 \\ -2 \end{pmatrix}

Thus, the equation of the plane is: 6(x11)4(x2+2)2(x33)=06(x_1 - 1) - 4(x_2 + 2) - 2(x_3 - 3) = 0 Expanding this: 6x164x282x3+6=06x_1 - 6 - 4x_2 - 8 - 2x_3 + 6 = 0 6x14x22x3=86x_1 - 4x_2 - 2x_3 = 8 Thus, the equation of the plane is: 6x14x22x3=86x_1 - 4x_2 - 2x_3 = 8

2. Intersection Point of the Plane EE and Line gg:

The line gg is given by: g:x=(123)+t(321),tRg: \vec{x} = \begin{pmatrix} -1 \\ -2 \\ -3 \end{pmatrix} + t \cdot \begin{pmatrix} -3 \\ 2 \\ 1 \end{pmatrix}, \quad t \in \mathbb{R}

To find the intersection point, substitute the parametric form of the line into the equation of the plane. The parametric equations for the line are: x1=13t,x2=2+2t,x3=3+tx_1 = -1 - 3t, \quad x_2 = -2 + 2t, \quad x_3 = -3 + t

Substitute these into the plane equation 6x14x22x3=86x_1 - 4x_2 - 2x_3 = 8: 6(13t)4(2+2t)2(3+t)=86(-1 - 3t) - 4(-2 + 2t) - 2(-3 + t) = 8 Expand and simplify: 618t+88t+62t=8-6 - 18t + 8 - 8t + 6 - 2t = 8 20t=8-20t = 8 t=25t = -\frac{2}{5}

Now substitute t=25t = -\frac{2}{5} back into the parametric equations for the line: x1=13(25)=1+65=55+65=15x_1 = -1 - 3\left(-\frac{2}{5}\right) = -1 + \frac{6}{5} = -\frac{5}{5} + \frac{6}{5} = \frac{1}{5} x2=2+2(25)=245=10545=145x_2 = -2 + 2\left(-\frac{2}{5}\right) = -2 - \frac{4}{5} = -\frac{10}{5} - \frac{4}{5} = -\frac{14}{5} x3=3+(25)=325=15525=175x_3 = -3 + \left(-\frac{2}{5}\right) = -3 - \frac{2}{5} = -\frac{15}{5} - \frac{2}{5} = -\frac{17}{5}

Thus, the intersection point is: P(15,145,175)P\left( \frac{1}{5}, -\frac{14}{5}, -\frac{17}{5} \right)


Would you like further clarifications or details? Here are some related questions:

  1. How do you find the parametric equation of a plane from its point-normal form?
  2. How does the cross product relate to the equation of a plane?
  3. What is the geometric interpretation of the intersection of a plane and a line?
  4. How would the solution change if the line was parallel to the plane?
  5. What if the system had no solution, meaning no intersection between the plane and line?

Tip: Always verify the normal vector of the plane by ensuring it is perpendicular to the given direction vectors.

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Math Problem Analysis

Mathematical Concepts

Vector Geometry
Parametric Form of Planes
Intersection of a Plane and Line

Formulas

Cross Product: n = v1 × v2
Equation of a Plane: Ax + By + Cz = D
Parametric Form of a Line: x = x0 + t * direction

Theorems

Vector Cross Product Theorem
Plane-Line Intersection Theorem

Suitable Grade Level

Undergraduate Level - Linear Algebra