Solve: D₁(r(t) = u(t)) X r(t) = 6ti - 4t³j + 5t²k u(t) = -2i+ 5t²j - 6t³k

Algebra & Trigonometry with Analytic Geometry
13th Edition
ISBN:9781133382119
Author:Swokowski
Publisher:Swokowski
Chapter9: Systems Of Equations And Inequalities
Section: Chapter Questions
Problem 39RE
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### Problem Statement

**Solve: \( D_t (\mathbf{r}(t) \times \mathbf{u}(t)) \)**

Given the vectors:

\[ \mathbf{r}(t) = 6t\mathbf{i} - 4t^3\mathbf{j} + 5t^2\mathbf{k} \]

\[ \mathbf{u}(t) = -2\mathbf{i} + 5t^2\mathbf{j} - 6t^3\mathbf{k} \]

### Explanation

We are tasked with finding the derivative of the cross product of two time-dependent vectors, \(\mathbf{r}(t)\) and \(\mathbf{u}(t)\).

#### Steps to Solve

1. **Calculate the Cross Product:**   
   \[
   \mathbf{r}(t) \times \mathbf{u}(t)
   \]

2. **Find the Derivative with Respect to \( t \):**   
   \[
   D_t (\mathbf{r}(t) \times \mathbf{u}(t))
   \]

### Detailed Steps

1. **Calculate \(\mathbf{r}(t) \times \mathbf{u}(t)\):**

Using the determinant form for the cross product of two vectors \(\mathbf{r}(t)\) and \(\mathbf{u}(t)\):

\[
\mathbf{r}(t) \times \mathbf{u}(t) = 
\begin{vmatrix}
\mathbf{i} & \mathbf{j} & \mathbf{k} \\
6t & -4t^3 & 5t^2 \\
-2 & 5t^2 & -6t^3
\end{vmatrix}
\]

Expanding this determinant:

\[
\mathbf{r}(t) \times \mathbf{u}(t) = \mathbf{i} \left( (-4t^3)(-6t^3) - (5t^2)(5t^2) \right) - \mathbf{j} \left( (6t)(-6t^3) - (5t^2)(-2) \right) + \mathbf{k} \left( (6t)(5t^2) - (-4t^3)(-2) \right)
\]

Simplify each component:

\[
= \mathbf{i}
Transcribed Image Text:### Problem Statement **Solve: \( D_t (\mathbf{r}(t) \times \mathbf{u}(t)) \)** Given the vectors: \[ \mathbf{r}(t) = 6t\mathbf{i} - 4t^3\mathbf{j} + 5t^2\mathbf{k} \] \[ \mathbf{u}(t) = -2\mathbf{i} + 5t^2\mathbf{j} - 6t^3\mathbf{k} \] ### Explanation We are tasked with finding the derivative of the cross product of two time-dependent vectors, \(\mathbf{r}(t)\) and \(\mathbf{u}(t)\). #### Steps to Solve 1. **Calculate the Cross Product:** \[ \mathbf{r}(t) \times \mathbf{u}(t) \] 2. **Find the Derivative with Respect to \( t \):** \[ D_t (\mathbf{r}(t) \times \mathbf{u}(t)) \] ### Detailed Steps 1. **Calculate \(\mathbf{r}(t) \times \mathbf{u}(t)\):** Using the determinant form for the cross product of two vectors \(\mathbf{r}(t)\) and \(\mathbf{u}(t)\): \[ \mathbf{r}(t) \times \mathbf{u}(t) = \begin{vmatrix} \mathbf{i} & \mathbf{j} & \mathbf{k} \\ 6t & -4t^3 & 5t^2 \\ -2 & 5t^2 & -6t^3 \end{vmatrix} \] Expanding this determinant: \[ \mathbf{r}(t) \times \mathbf{u}(t) = \mathbf{i} \left( (-4t^3)(-6t^3) - (5t^2)(5t^2) \right) - \mathbf{j} \left( (6t)(-6t^3) - (5t^2)(-2) \right) + \mathbf{k} \left( (6t)(5t^2) - (-4t^3)(-2) \right) \] Simplify each component: \[ = \mathbf{i}
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