Find the area of a triangle PQR, where P = (6, 3, 5), Q = (0,4, -3), and R=(-6, -1, - 5)

Calculus: Early Transcendentals
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Author:James Stewart
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Chapter1: Functions And Models
Section: Chapter Questions
Problem 1RCC: (a) What is a function? What are its domain and range? (b) What is the graph of a function? (c) How...
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**Problem Statement:**

Find the area of a triangle \(PQR\), where \(P = (6, -3, -5)\), \(Q = (0, 4, -3)\), and \(R = (-6, -1, -5)\).

**Explanation:**

To find the area of the triangle \(PQR\), where the vertices are given in three dimensions, we use the vector cross product method. The formula for the area of a triangle with vertices \(P\), \(Q\), and \(R\) is given by:

\[ \text{Area} = \frac{1}{2} \| \overrightarrow{PQ} \times \overrightarrow{PR} \| \]

1. **Calculating Vectors:**
   - Vector \(\overrightarrow{PQ}\):
     \[ \overrightarrow{PQ} = Q - P = (0 - 6, 4 - (-3), -3 - (-5)) = (-6, 7, 2) \]

   - Vector \(\overrightarrow{PR}\):
     \[ \overrightarrow{PR} = R - P = (-6 - 6, -1 - (-3), -5 - (-5)) = (-12, 2, 0) \]

2. **Cross Product of Vectors \(\overrightarrow{PQ}\) and \(\overrightarrow{PR}\):**
   - Using the determinant method to find the cross product \(\overrightarrow{PQ} \times \overrightarrow{PR}\), we get:
     \[
     \overrightarrow{PQ} \times \overrightarrow{PR} = \begin{vmatrix}
     \mathbf{i} & \mathbf{j} & \mathbf{k} \\
     -6 & 7 & 2 \\
     -12 & 2 & 0
     \end{vmatrix}
     \]

   - Expanding the determinant:
     \[
     = \mathbf{i}(7 \cdot 0 - 2 \cdot 2) - \mathbf{j}(-6 \cdot 0 - 2 \cdot -12) + \mathbf{k}(-6 \cdot 2 - 7 \cdot -12)
     \]
     \[
     = \mathbf{i}(0 - 4) - \mathbf{j}(0 +
Transcribed Image Text:**Problem Statement:** Find the area of a triangle \(PQR\), where \(P = (6, -3, -5)\), \(Q = (0, 4, -3)\), and \(R = (-6, -1, -5)\). **Explanation:** To find the area of the triangle \(PQR\), where the vertices are given in three dimensions, we use the vector cross product method. The formula for the area of a triangle with vertices \(P\), \(Q\), and \(R\) is given by: \[ \text{Area} = \frac{1}{2} \| \overrightarrow{PQ} \times \overrightarrow{PR} \| \] 1. **Calculating Vectors:** - Vector \(\overrightarrow{PQ}\): \[ \overrightarrow{PQ} = Q - P = (0 - 6, 4 - (-3), -3 - (-5)) = (-6, 7, 2) \] - Vector \(\overrightarrow{PR}\): \[ \overrightarrow{PR} = R - P = (-6 - 6, -1 - (-3), -5 - (-5)) = (-12, 2, 0) \] 2. **Cross Product of Vectors \(\overrightarrow{PQ}\) and \(\overrightarrow{PR}\):** - Using the determinant method to find the cross product \(\overrightarrow{PQ} \times \overrightarrow{PR}\), we get: \[ \overrightarrow{PQ} \times \overrightarrow{PR} = \begin{vmatrix} \mathbf{i} & \mathbf{j} & \mathbf{k} \\ -6 & 7 & 2 \\ -12 & 2 & 0 \end{vmatrix} \] - Expanding the determinant: \[ = \mathbf{i}(7 \cdot 0 - 2 \cdot 2) - \mathbf{j}(-6 \cdot 0 - 2 \cdot -12) + \mathbf{k}(-6 \cdot 2 - 7 \cdot -12) \] \[ = \mathbf{i}(0 - 4) - \mathbf{j}(0 +
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