Chapter 2: Problem 21
Prove that \(C\) is on the perpendicular bisector of segment \(A B\) $$A(-4,-3), \quad B(6,1), \quad C(5,-11)$$
Short Answer
Expert verified
Point C is on the perpendicular bisector of segment AB.
Step by step solution
01
Find the Midpoint of Segment AB
The midpoint of a segment with endpoints \((x_1,y_1), (x_2, y_2)\) is given by the formula: \[ \left( \frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2} \right) \.\] Plugging in the coordinates of points \(A\) and \(B\), we have \[ \left( \frac{-4 + 6}{2}, \frac{-3 + 1}{2} \right) = (1, -1).\] The midpoint of \(AB\) is thus \((1, -1)\).
02
Calculate the Slope of Segment AB
The slope of a line through two points \((x_1, y_1), (x_2, y_2)\) is given by: \[ m = \frac{y_2 - y_1}{x_2 - x_1} \.\] For segment \(AB\), calculate \[ m = \frac{1 - (-3)}{6 - (-4)} = \frac{1 + 3}{6 + 4} = \frac{4}{10} = \frac{2}{5}.\] The slope of \(AB\) is \(\frac{2}{5}\).
03
Determine the Slope of the Perpendicular Bisector
The slope of the perpendicular bisector is the negative reciprocal of the slope of \(AB\). Since the slope of \(AB\) is \(\frac{2}{5}\), the slope of the perpendicular bisector is \(-\frac{5}{2}\).
04
Verify that Point C Lies on the Perpendicular Bisector
To check if \(C\) lies on the line with slope \(-\frac{5}{2}\) and passing through the midpoint \((1, -1)\), use the point-slope form of the equation of a line: \[ y - y_1 = m(x - x_1), \] where \(m = -\frac{5}{2}, (x_1, y_1) = (1, -1)\). This gives \[ y + 1 = -\frac{5}{2}(x - 1). \] Simplifying, \[ y + 1 = -\frac{5}{2}x + \frac{5}{2}. \] Therefore, \[ y = -\frac{5}{2}x + \frac{5}{2} - 1, \] \[ y = -\frac{5}{2}x + \frac{3}{2}. \] Substitute \(x = 5\) and \(y = -11\) to check point \(C\): \[ -11 = -\frac{5}{2}(5) + \frac{3}{2}. \] This simplifies to \[ -11 = -\frac{25}{2} + \frac{3}{2} = -\frac{22}{2} = -11.\] Thus, \(C(5, -11)\) satisfies the line equation.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Midpoint Formula
The midpoint formula is a simple tool in coordinate geometry to find the center point of a line segment. Imagine you have a segment with two given endpoints. The midpoint is located exactly halfway, right between these two endpoints.
To find this midpoint, use the formula:
To find this midpoint, use the formula:
- Take the average of the x-coordinates: \(x_{mid} = rac{x_1 + x_2}{2}\)
- Take the average of the y-coordinates: \(y_{mid} = rac{y_1 + y_2}{2}\)
- Midpoint x-coordinate: \( rac{-4 + 6}{2} = 1 \)
- Midpoint y-coordinate: \( rac{-3 + 1}{2} = -1 \)
Slope Calculation
Understanding the slope of a line is fundamental in coordinate geometry. It tells you how steep the line is. By calculating the slope, you discover how much the y-coordinate changes with the x-coordinate.
The formula to find the slope \( m \) between two points is:
The formula to find the slope \( m \) between two points is:
- Vertical change: \( ext{rise} = y_2 - y_1 \)
- Horizontal change: \( ext{run} = x_2 - x_1 \)
- Slope: \( m = rac{ ext{rise}}{ ext{run}} \)
- Rise: \( 1 - (-3) = 4 \)
- Run: \( 6 - (-4) = 10 \)
- Slope: \( m = rac{4}{10} = rac{2}{5} \)
Perpendicular Bisector
A perpendicular bisector is a line that divides another line segment into two equal parts at a right angle. Why is it so special? Because if another point is equidistant from the endpoints of this segment, it will lie on this bisector.
To find the equation of a perpendicular bisector:
To find the equation of a perpendicular bisector:
- Determine the midpoint of the segment using the midpoint formula. We've already done this, finding it to be \( (1, -1) \).
- Find the slope of the original segment. For our segment AB, it’s \( rac{2}{5} \).
- The perpendicular bisector has the negative reciprocal slope. So, switch the numerator with the denominator and change the sign: \( -rac{5}{2} \).
Equation of a Line
The equation of a line, especially in point-slope form, is crucial for showing where a line goes on a graph given one point and its slope.
To form a line equation, we use:
To form a line equation, we use:
- Point-Slope Formula: \( y - y_1 = m(x - x_1) \)
- Here, \( (x_1, y_1) \) is a known point, and \( m \) is the slope.
- Starting Point-Slope: \( y + 1 = -\frac{5}{2}(x - 1) \)
- Solving gives: \( y = -\frac{5}{2}x + \frac{3}{2} \)
- If both sides equal, then C is on the line, confirming its location on the bisector.