Chapter 5: Problem 24
Find the distance from the given point \(P\) to the given line \(L\). \(P(-6,4) ;\) Line \(L\) with equation \(x-y=3\)
Short Answer
Expert verified
The distance from the point \(P(-6,4)\) to the line \(L\) with equation \(x-y=3\) is \( \frac{13\sqrt{2}}{2} \).
Step by step solution
01
Rewrite the line equation
Since we are given the line equation as \(x-y=3\), we can rewrite it as the general form of a line equation: \(Ax + By + C = 0\). In our case, we have \(A=1\), \(B=-1\), and \(C=-3\). So the general form of our line equation becomes \(1\cdot x - 1\cdot y - 3 = 0\).
02
Apply the distance formula
To find the distance from the point P to the line L, we make use of the following distance formula:
\( d = \frac{|Ax_{1} + By_{1} + C|}{\sqrt{A^2 + B^2}} \)
Plugging in our values from the given point \(P(-6,4)\) and our line with coefficients \(A=1\), \(B=-1\), \(C=-3\), we get:
\( d = \frac{|1\cdot(-6) - 1\cdot4 - 3|}{\sqrt{1^2 + (-1)^2}} \)
03
Solve for the distance
Now, we can solve for the distance:
\( d = \frac{|-6 - 4 - 3|}{\sqrt{1^2 + (-1)^2}} = \frac{|-13|}{\sqrt{2}} = \frac{13}{\sqrt{2}} \)
Now, we can rationalize the denominator:
\( d = \frac{13\sqrt{2}}{2} \)
So the distance from the point \(P(-6,4)\) to the line \(L\) with equation \(x-y=3\) is \( \frac{13\sqrt{2}}{2} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Distance Formula
The distance formula is a powerful mathematical tool that helps us determine the distance between a point and a line. It is given by: \[d = \frac{|Ax_{1} + By_{1} + C|}{\sqrt{A^2 + B^2}} \] This formula uses the coefficients from the line's equation in its general form: \(Ax + By + C = 0\), and the coordinates from the point \(P(x_1, y_1)\). Understanding how this formula works is essential:
- The numerator \(|Ax_{1} + By_{1} + C|\) calculates the absolute value of the linear expression for the given point, determining how far the point stands from the line in a direction perpendicular to it.
- The denominator \(\sqrt{A^2 + B^2}\) normalizes this distance in terms of the coefficients of the line, essentially giving the length of the perpendicular distance from the point to the line in a unitless form.
Line Equation
To use the distance formula effectively, we must first express our line in its general form, which takes the structure \(Ax + By + C = 0\). For instance, the line \(x-y=3\) should be rewritten to align with this form: \(1 \cdot x - 1 \cdot y - 3 = 0\), where \(A=1\), \(B=-1\), and \(C=-3\).
- This standardization is critical so the coefficients can be comfortably used with the distance formula.
- Once transformed into this form, it offers us a systematic way to plug into related equations and solve real-world geometry problems easier.
Point-Line Distance
Determining the point-line distance involves calculating how far a given point is from a specified line. This type of problem typically engages the distance formula to achieve accurate results. If we use a point \(P(-6,4)\) and a line with equation \(x-y=3\):
- Substitute \(x = -6\) and \(y = 4\) into the absolute value expression \(|Ax_{1} + By_{1} + C|\). For our example, this becomes: \[ |-6 - 4 - 3| = |-13| = 13 \]
- Compute the denominator \(\sqrt{A^2 + B^2}\), which in this case is: \[ \sqrt{1^2 + (-1)^2} = \sqrt{2} \]
Rationalizing the Denominator
Rationalizing the denominator is a helpful algebraic technique that involves adjusting the expression so that the denominator becomes a simple rational number. When we have a distance \( \frac{13}{\sqrt{2}} \), the radical \(\sqrt{2}\) in the denominator makes it less clean for precise applications.
- We multiply the numerator and the denominator by \(\sqrt{2}\) to eliminate the root from the denominator and maintain the value's equality: \[ \frac{13}{\sqrt{2}} \times \frac{\sqrt{2}}{\sqrt{2}} = \frac{13\sqrt{2}}{2} \]
- This results in \(\frac{13\sqrt{2}}{2}\), a neater form convenient for additional calculations or discussions.