Chapter 9: Problem 1
Determine the distance from \(P(-4,5)\) to each of the following lines: a. \(3 x+4 y-5=0\) b. \(5 x-12 y+24=0\) c. \(9 x-40 y=0\)
Short Answer
Expert verified
The distances are 0.6 to line a, approximately 4.308 to line b, and approximately 5.756 to line c.
Step by step solution
01
Understanding the Point-to-Line Distance Formula
The distance from a point \(P(x_1, y_1)\) to a line of the form \(Ax + By + C = 0\) can be found using the formula: \[ d = \frac{|Ax_1 + By_1 + C|}{\sqrt{A^2 + B^2}} \] This formula calculates the perpendicular distance from the point to the line.
02
Identify Parameters for Line a
For the line \(3x + 4y - 5 = 0\), we identify \(A = 3\), \(B = 4\), and \(C = -5\). The coordinates of the point \(P\) are \((-4, 5)\).
03
Calculate Distance for Line a
Substitute the values into the distance formula: \[ d_a = \frac{|3(-4) + 4(5) - 5|}{\sqrt{3^2 + 4^2}} \] Calculate inside the absolute value: \[ 3(-4) + 4(5) - 5 = -12 + 20 - 5 = 3 \] Find the distance: \[ d_a = \frac{|3|}{\sqrt{9 + 16}} = \frac{3}{\sqrt{25}} = \frac{3}{5} = 0.6 \]
04
Identify Parameters for Line b
For the line \(5x - 12y + 24 = 0\), we identify \(A = 5\), \(B = -12\), and \(C = 24\). The coordinates of the point \(P\) are \((-4, 5)\).
05
Calculate Distance for Line b
Substitute the values into the distance formula: \[ d_b = \frac{|5(-4) - 12(5) + 24|}{\sqrt{5^2 + (-12)^2}} \] Calculate inside the absolute value: \[ 5(-4) - 12(5) + 24 = -20 - 60 + 24 = -56 \] Find the distance: \[ d_b = \frac{|-56|}{\sqrt{25 + 144}} = \frac{56}{\sqrt{169}} = \frac{56}{13} \approx 4.308 \]
06
Identify Parameters for Line c
For the line \(9x - 40y = 0\), we identify \(A = 9\), \(B = -40\), and \(C = 0\). The coordinates of the point \(P\) are \((-4, 5)\).
07
Calculate Distance for Line c
Substitute the values into the distance formula: \[ d_c = \frac{|9(-4) - 40(5) + 0|}{\sqrt{9^2 + (-40)^2}} \] Calculate inside the absolute value:\[ 9(-4) - 40(5) = -36 - 200 = -236 \] Find the distance: \[ d_c = \frac{|-236|}{\sqrt{81 + 1600}} = \frac{236}{\sqrt{1681}} = \frac{236}{41} \approx 5.756 \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Point-to-Line Distance Formula
The Point-to-Line Distance Formula is a powerful tool in geometry. It helps us find the shortest distance from a point to a line. This distance is always measured along the line that is perpendicular to the given line and passes through the point.
The formula to calculate this distance is: \[ d = \frac{|Ax_1 + By_1 + C|}{\sqrt{A^2 + B^2}} \] Here,
The formula to calculate this distance is: \[ d = \frac{|Ax_1 + By_1 + C|}{\sqrt{A^2 + B^2}} \] Here,
- \((x_1, y_1)\) are the coordinates of the point for which you're finding the distance.
- \(A\), \(B\), and \(C\) are the coefficients from the line equation, generally presented as \(Ax + By + C = 0\).
Perpendicular Distance
Perpendicular distance is a key concept when talking about distances in geometry. Imagine dropping a straight line from a point to a line that is perpendicular to the line. This shortest path is the perpendicular distance.
**Why Perpendicular?**
**Why Perpendicular?**
- It's the shortest path. Any slanted or non-perpendicular line is longer.
- It aligns with the orthogonality of Cartesian coordinates, providing a clear, exact measure.
Cartesian Coordinates
Cartesian Coordinates are an essential part of analytical geometry, named after René Descartes. It relies on two perpendicular axes: the horizontal (x-axis) and the vertical (y-axis). They help in identifying the position of a point by determining how far along each axis a point is positioned.
**Key Elements:**
**Key Elements:**
- **Origin**: The point (0, 0), where the two axes intersect.
- **Coordinates**: A pair \((x, y)\) that specifies the location with respect to the axes.
- **Quadrants**: The two-dimensional plane is divided into four quadrants, aiding spatial understanding.
Analytical Geometry
Analytical Geometry, also known as coordinate geometry, is a branch of mathematics that uses algebra to understand and explore the geometry of figures. It is incredibly useful for solving geometric problems algebraically, as it provides a clear framework to represent geometric figures as equations.
**Benefits and Uses**:
**Benefits and Uses**:
- Combines the spatial visualization of geometry with the logical precision of algebra.
- Allows complex geometry problems to be broken down into manageable algebraic tasks.
- Facilitates understanding of distances, gradients, and relationships between geometric entities.