Chapter 12: Problem 36
In Exercises \(35-38\) , find a. the direction of \(P_{1} P_{2}\) and b. the midpoint of line segment \(P_{1} P_{2}\) . $$ P_{1}(1,4,5) \quad P_{2}(4,-2,7) $$
Short Answer
Expert verified
a. The direction is \((3, -6, 2)\). b. The midpoint is \(\left( \frac{5}{2}, 1, 6 \right)\).
Step by step solution
01
Calculate the Direction of \(P_{1} P_{2}\)
To find the direction of line segment \(P_{1} P_{2}\), calculate the difference between the coordinates of points \(P_{2}\) and \(P_{1}\). The direction is given by the vector \(\overrightarrow{P_{1}P_{2}} = (x_2 - x_1, y_2 - y_1, z_2 - z_1)\). Substitute the coordinates of \(P_{1}(1,4,5)\) and \(P_{2}(4,-2,7)\): \[\overrightarrow{P_{1}P_{2}} = (4 - 1, -2 - 4, 7 - 5) = (3, -6, 2).\]
02
Calculate the Midpoint of Line Segment \(P_{1} P_{2}\)
The midpoint of a line segment \(P_{1} P_{2}\) is calculated using the formula: \[M = \left( \frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2}, \frac{z_1 + z_2}{2} \right).\] Substitute the given points: \[M = \left( \frac{1 + 4}{2}, \frac{4 - 2}{2}, \frac{5 + 7}{2} \right) = \left( \frac{5}{2}, 1, 6 \right).\]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Direction Vectors
In vector calculus, a direction vector is a crucial concept used to describe the direction of a line or line segment. In the context of 3D coordinate geometry, a direction vector can be determined by finding the differences between the corresponding coordinates of two points. The process can be thought of as creating a vector that "points" from one location to another. Here’s how you can find it:
- Identify the coordinates: Begin by noting the coordinates of the two points. For example, if you have points \(P_1(1, 4, 5)\) and \(P_2(4, -2, 7)\), your task is to calculate the direction vector between them.
- Calculate the differences: Subtract each coordinate of point \(P_1\) from the corresponding coordinate of point \(P_2\). This will give you the direction vector \(\overrightarrow{P_1P_2} = (x_2 - x_1, y_2 - y_1, z_2 - z_1)\).
- Example: Using our points \(P_1\) and \(P_2\), you get the direction vector \((3, -6, 2)\), derived as follows: \(\overrightarrow{P_{1}P_{2}} = (4 - 1, -2 - 4, 7 - 5)\).
The Midpoint Formula in 3D
The midpoint formula is a simple yet powerful tool in geometry, especially for finding the point that lies directly between two other points in space. When working with three-dimensional coordinate geometry, the midpoint \(M\) of a line segment joining points \(P_1(x_1, y_1, z_1)\) and \(P_2(x_2, y_2, z_2)\) is derived using the formula:
- Sum the coordinates: First, add the corresponding coordinates of the two points, meaning the \(x\), \(y\), and \(z\) values.
- Divide by two: Next, divide each of these sums by 2 to find the midpoint’s coordinate values. This step calculates the average position between the two points along each axis.
- Example: For points \(P_1(1, 4, 5)\) and \(P_2(4, -2, 7)\), the midpoint would be \(M = \left( \frac{1 + 4}{2}, \frac{4 + (-2)}{2}, \frac{5 + 7}{2} \right)\).
- Final Result: Calculating these gives \(M = \left( \frac{5}{2}, 1, 6 \right)\), nicely placing \(M\) halfway between \(P_1\) and \(P_2\).
Exploring 3D Coordinate Geometry
3D coordinate geometry expands upon the familiar concepts from 2D geometry by adding an additional axis, typically labeled as the \(z\)-axis, complementing the \(x\) and \(y\)-axes. This creates a three-dimensional space where every point is indicated by three numbers, \((x, y, z)\). Here's a closer look at its fundamental aspects:
- The Coordinate System: In 3D, the coordinate system consists of three axes—\(x\), \(y\), and \(z\)—that intersect at a point called the origin. Every other point in this space is described relative to the origin.
- Visualizing Points and Lines: Points are denoted by their coordinates \((x, y, z)\), while lines or vectors between points are often represented in component form, such as \((x_2 - x_1, y_2 - y_1, z_2 - z_1)\), providing both magnitude and direction.
- Applications: This dimension is crucial in fields requiring spatial analysis like physics, engineering, and computer graphics, where real-world scenarios often occur in three dimensions.
- Example: Given points like \(P_1(1, 4, 5)\) and \(P_2(4, -2, 7)\), one can calculate distances, directions, or midpoints, using formulas adapted for an additional dimension.