Math Problem Statement

Find the distance between the point and the line given by the set of parametric equations. (Round your answer to three decimal places.) (1, -1, 5); x = 2t, y = t − 3, z = 2t + 2

Solution

To find the distance between a point and a line given by parametric equations, we'll use the following steps:

  1. Express the line in vector form: The parametric equations for the line are: x=2t,y=t3,z=2t+2x = 2t, \quad y = t - 3, \quad z = 2t + 2 This can be written as: r(t)=(2t,t3,2t+2)\mathbf{r}(t) = (2t, t - 3, 2t + 2) The direction vector v\mathbf{v} of the line is given by the coefficients of tt: v=2,1,2\mathbf{v} = \langle 2, 1, 2 \rangle A point on the line when t=0t = 0 is: r0=(0,3,2)\mathbf{r}_0 = (0, -3, 2)

  2. Find the vector from the point to a point on the line: Let the given point be P=(1,1,5)\mathbf{P} = (1, -1, 5). The vector from r0\mathbf{r}_0 to P\mathbf{P} is: Pr0=10,1(3),52=1,2,3\mathbf{P} - \mathbf{r}_0 = \langle 1 - 0, -1 - (-3), 5 - 2 \rangle = \langle 1, 2, 3 \rangle

  3. Compute the cross product of this vector with the direction vector: The cross product v×(Pr0)\mathbf{v} \times (\mathbf{P} - \mathbf{r}_0) is: v×1,2,3=ijk212123\mathbf{v} \times \langle 1, 2, 3 \rangle = \begin{vmatrix} \mathbf{i} & \mathbf{j} & \mathbf{k} \\ 2 & 1 & 2 \\ 1 & 2 & 3 \end{vmatrix} =i(1322)j(2321)+k(2211)= \mathbf{i} \left(1 \cdot 3 - 2 \cdot 2\right) - \mathbf{j} \left(2 \cdot 3 - 2 \cdot 1\right) + \mathbf{k} \left(2 \cdot 2 - 1 \cdot 1\right) =i(34)j(62)+k(41)= \mathbf{i} (3 - 4) - \mathbf{j} (6 - 2) + \mathbf{k} (4 - 1) =1,4,3= \langle -1, -4, 3 \rangle

  4. Calculate the magnitude of the cross product: v×(Pr0)=(1)2+(4)2+32=1+16+9=26|\mathbf{v} \times (\mathbf{P} - \mathbf{r}_0)| = \sqrt{(-1)^2 + (-4)^2 + 3^2} = \sqrt{1 + 16 + 9} = \sqrt{26}

  5. Compute the magnitude of the direction vector: v=22+12+22=4+1+4=9=3|\mathbf{v}| = \sqrt{2^2 + 1^2 + 2^2} = \sqrt{4 + 1 + 4} = \sqrt{9} = 3

  6. Calculate the distance: The distance dd from the point to the line is given by: d=v×(Pr0)v=263d = \frac{|\mathbf{v} \times (\mathbf{P} - \mathbf{r}_0)|}{|\mathbf{v}|} = \frac{\sqrt{26}}{3} d5.09931.700d \approx \frac{5.099}{3} \approx 1.700

So, the distance between the point (1,1,5)(1, -1, 5) and the line is approximately 1.7001.700 units.

Would you like more details or have any questions?

Here are some related questions:

  1. How is the cross product of two vectors calculated?
  2. What is the significance of the magnitude of a vector?
  3. How can you derive the distance formula from a point to a line?
  4. What are the parametric equations of a line in three-dimensional space?
  5. How does the direction vector of a line relate to its parametric equations?
  6. Can the distance between a point and a line ever be negative?
  7. What role does the dot product play in geometry?
  8. How do you find the shortest distance between two skew lines?

Tip: Always verify your vector calculations step by step to avoid errors, especially in cross products.

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Math Problem Analysis

Mathematical Concepts

Vectors
Parametric Equations
Cross Product
Distance Formula

Formulas

Distance between a point and a line formula

Theorems

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Suitable Grade Level

Advanced High School