Math Problem Statement

Find the area of the parallelogram that has u and v as adjacent sides.

u = −i + 2j − 2k

v = i + k    square units

Solution

To find the area of the parallelogram formed by vectors u\mathbf{u} and v\mathbf{v}, we need to compute the magnitude of their cross product.

Given vectors: u=i+2j2k=(122)\mathbf{u} = -\mathbf{i} + 2\mathbf{j} - 2\mathbf{k} = \begin{pmatrix} -1 \\ 2 \\ -2 \end{pmatrix} v=i+k=(101)\mathbf{v} = \mathbf{i} + \mathbf{k} = \begin{pmatrix} 1 \\ 0 \\ 1 \end{pmatrix}

First, compute the cross product u×v\mathbf{u} \times \mathbf{v}: u×v=ijk122101\mathbf{u} \times \mathbf{v} = \begin{vmatrix} \mathbf{i} & \mathbf{j} & \mathbf{k} \\ -1 & 2 & -2 \\ 1 & 0 & 1 \end{vmatrix}

Expanding this determinant: u×v=i(21(2)0)j(11(2)1)+k(1021)\mathbf{u} \times \mathbf{v} = \mathbf{i} \left( 2 \cdot 1 - (-2) \cdot 0 \right) - \mathbf{j} \left( -1 \cdot 1 - (-2) \cdot 1 \right) + \mathbf{k} \left( -1 \cdot 0 - 2 \cdot 1 \right)

Simplify each component: i(20)j(1+2)+k(02)\mathbf{i} (2 - 0) - \mathbf{j} (-1 + 2) + \mathbf{k} (0 - 2) =i(2)j(1)+k(2)= \mathbf{i} (2) - \mathbf{j} (1) + \mathbf{k} (-2)

Thus, the cross product is: u×v=(212)\mathbf{u} \times \mathbf{v} = \begin{pmatrix} 2 \\ -1 \\ -2 \end{pmatrix}

Next, find the magnitude of this vector to determine the area of the parallelogram: u×v=22+(1)2+(2)2\left| \mathbf{u} \times \mathbf{v} \right| = \sqrt{2^2 + (-1)^2 + (-2)^2} =4+1+4= \sqrt{4 + 1 + 4} =9= \sqrt{9} =3= 3

So, the area of the parallelogram is: 3 square units3 \text{ square units}

Would you like any further details or have any questions?

Here are 8 related questions you might find interesting:

  1. How do you find the area of a parallelogram in two dimensions?
  2. How do you determine if two vectors are parallel?
  3. What is the geometric meaning of the determinant of a matrix in two or three dimensions?
  4. How can you find the volume of a parallelepiped using vectors?
  5. What is the triple product of vectors, and how is it related to volume?
  6. How do you normalize a vector, and why is it useful?
  7. What is the significance of the vector projection in physical applications?
  8. How do you use vector addition to solve problems involving forces?

Tip: Remember, the cross product's direction follows the right-hand rule, which can help visualize the perpendicular vector in three-dimensional space.

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Math Problem Analysis

Mathematical Concepts

Vectors
Cross Product
Magnitude

Formulas

Cross product formula
Magnitude of a vector formula

Theorems

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Suitable Grade Level

Advanced High School