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Perpendicular Bisector

This calculator helps you find the equation of the perpendicular bisector of a line segment defined by two points. A perpendicular bisector is a line that cuts a segment exactly in half at a 90-degree angle.

Enter the x-coordinate of the first point.

Enter the y-coordinate of the first point.

Enter the x-coordinate of the second point.

Enter the y-coordinate of the second point.

How it works

This calculator helps you find the equation of the perpendicular bisector of a line segment defined by two points. A perpendicular bisector is a line that cuts a segment exactly in half at a 90-degree angle.


The Formula
To find the perpendicular bisector, we first calculate the midpoint of the segment using M = ((x1+x2)/2, (y1+y2)/2). Then, we find the slope of the segment, m = (y2-y1)/(x2-x1). The perpendicular slope is -1/m. Finally, we use the point-slope form (y - y_m = m_perp * (x - x_m)) to get the equation of the bisector.

Worked Example
  1. Example: Points (1, 2) and (5, 6)

    Let's find the perpendicular bisector for points A(1, 2) and B(5, 6). 1. Midpoint: ((1+5)/2, (2+6)/2) = (3, 4). 2. Slope of AB: (6-2)/(5-1) = 4/4 = 1. 3. Perpendicular slope: -1/1 = -1. 4. Using point-slope form with midpoint (3, 4) and slope -1: y - 4 = -1(x - 3) => y - 4 = -x + 3 => y = -x + 7. So, the perpendicular bisector is y = -x + 7.


Tips, Assumptions & Limitations
  • Ensure your coordinates are entered correctly for both points.
  • Remember that a vertical segment will have a horizontal bisector (y = constant), and a horizontal segment will have a vertical bisector (x = constant).
  • The perpendicular bisector is equidistant from the two original points.
FAQ

A perpendicular bisector is a line that intersects a given line segment at its midpoint and forms a 90-degree angle with it. Every point on the perpendicular bisector is equidistant from the two endpoints of the original segment.

First, find the midpoint of the segment. Second, calculate the slope of the segment. Third, determine the negative reciprocal of that slope to get the perpendicular slope. Finally, use the point-slope form of a linear equation (y - y1 = m(x - x1)) with the midpoint and the perpendicular slope to find the equation of the bisector.

Yes, the calculator is designed to correctly identify and calculate the perpendicular bisector for vertical segments (resulting in a horizontal line, e.g., y = constant) and horizontal segments (resulting in a vertical line, e.g., x = constant).

Companion article

Perpendicular Bisector Calculator: Find the Equation of a Dividing Line

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