Math Problem Statement

Find the distance from the point (3, -7, -3) to the line \(\vec{a}(t) = \langle -5, -3, 0 \rangle t + \langle -7, 3, -5 \rangle\).

Solution

The problem asks to find the distance from the point (3,7,3)(3, -7, -3) to the line a(t)=5,3,0t+7,3,5\vec{a}(t) = \langle -5, -3, 0 \rangle t + \langle -7, 3, -5 \rangle.

Steps to solve:

  1. Point on the Line: The parametric equation of the line is given by: a(t)=5,3,0t+7,3,5=5t7,3t+3,5.\vec{a}(t) = \langle -5, -3, 0 \rangle t + \langle -7, 3, -5 \rangle = \langle -5t - 7, -3t + 3, -5 \rangle. Here, the point on the line depends on the parameter tt.

  2. Direction Vector of the Line: The direction vector of the line is 5,3,0\langle -5, -3, 0 \rangle.

  3. Vector from Point to a Point on the Line: The point (3,7,3)(3, -7, -3) is not on the line. To find the vector from this point to a specific point on the line (say when t=0t = 0, a(0)=7,3,5\vec{a}(0) = \langle -7, 3, -5 \rangle), we can calculate the vector: v=3,7,37,3,5=3+7,73,3+5=10,10,2.\vec{v} = \langle 3, -7, -3 \rangle - \langle -7, 3, -5 \rangle = \langle 3 + 7, -7 - 3, -3 + 5 \rangle = \langle 10, -10, 2 \rangle.

  4. Projection of Vector onto the Line: The formula for the distance between a point and a line in 3D is given by: d=v×dd,d = \frac{|\vec{v} \times \vec{d}|}{|\vec{d}|}, where v=10,10,2\vec{v} = \langle 10, -10, 2 \rangle is the vector from the point to a point on the line, and d=5,3,0\vec{d} = \langle -5, -3, 0 \rangle is the direction vector of the line.

  5. Cross Product: Let's compute the cross product v×d\vec{v} \times \vec{d}:

    = \hat{i} ( (-10)(0) - (-3)(2) ) - \hat{j} ( (10)(0) - (-5)(2) ) + \hat{k} ( (10)(-3) - (-10)(-5) )$$ $$= \hat{i}(6) - \hat{j}(-10) + \hat{k}(-30 - 50) = \langle 6, 10, -80 \rangle.$$
  6. Magnitude of the Cross Product: Now, calculate the magnitude of v×d\vec{v} \times \vec{d}: v×d=62+102+(80)2=36+100+6400=6536.|\vec{v} \times \vec{d}| = \sqrt{6^2 + 10^2 + (-80)^2} = \sqrt{36 + 100 + 6400} = \sqrt{6536}.

  7. Magnitude of the Direction Vector: The magnitude of the direction vector d=5,3,0\vec{d} = \langle -5, -3, 0 \rangle is: d=(5)2+(3)2+02=25+9=34.|\vec{d}| = \sqrt{(-5)^2 + (-3)^2 + 0^2} = \sqrt{25 + 9} = \sqrt{34}.

  8. Final Distance: Now, the distance dd is: d=v×dd=653634=653634=19213.86.d = \frac{|\vec{v} \times \vec{d}|}{|\vec{d}|} = \frac{\sqrt{6536}}{\sqrt{34}} = \sqrt{\frac{6536}{34}} = \sqrt{192} \approx 13.86.

The distance from the point (3,7,3)(3, -7, -3) to the line is approximately 13.86 units.

Would you like a deeper breakdown or explanation of any steps?

Here are 5 related questions to deepen your understanding:

  1. How do you find the equation of a line in 3D space?
  2. What is the geometric interpretation of the cross product?
  3. How do you project a vector onto another vector in 3D?
  4. What is the formula for the distance between two parallel lines?
  5. How can you compute the shortest distance from a point to a plane?

Tip: For vector calculations like cross products, visualizing the vectors helps in understanding the spatial relationships better.

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Math Problem Analysis

Mathematical Concepts

Vector Algebra
3D Geometry
Cross Product

Formulas

Distance from a point to a line: \(d = \frac{|\vec{v} \times \vec{d}|}{|\vec{d}|}\)
Cross product of vectors: \(\vec{v} \times \vec{d}\)
Magnitude of a vector: \(|\vec{v}| = \sqrt{v_x^2 + v_y^2 + v_z^2}\)

Theorems

Cross Product Theorem
Distance Formula in 3D

Suitable Grade Level

Undergraduate Level