Perpendicular Bisector Theorem

A point is equidistant from other points if it is the same distance from them.

The Perpendicular Bisector Theorem states that a point is on the perpendicular bisector of a segment if and only if it is equidistant from the endpoints of the segment.

X is on the perpendicular bisector of WY if and only if WX ≅ XY .

Definition:

The Perpendicular Bisector Theorem is a geometric principle that relates to a line segment and its perpendicular bisector.

Statement:

If a point lies on the perpendicular bisector of a segment, then it is equidistant from the endpoints of the segment.

Key Concepts:

  1. Perpendicular Bisector:
    • A line, segment, or ray that intersects another line segment at its midpoint and forms a right angle (90 degrees) with the segment.
  2. Equidistant:
    • The distance from a point to each endpoint of a segment is equal.

Theorem Statement:

If a point P lies on the perpendicular bisector of segment AB, then PA=PB, where PA and PB are the distances from point P to the endpoints A and B respectively.

Example:

Consider line segment AB with midpoint M. If P is a point on the perpendicular bisector of AB, then PM=PA=PB.

Learn with an example

GI= ______________

Look at the diagram.

since GH = HI = 84 , H  is equidistant from the endpoints of GI . Therefore H lies on the perpendicular bisector of GI by the Perpendicular Bisector Theorem.

Since H is on the perpendicular bisector of GI and HJI is a right angle ,HJ  is the perpendicular bisector of GI .

So, GJ = IJ = 69 and G . I = 2.69 = 138.

QR=_____________

Look at the diagram.

Since ∠QPR is a right angle and PQ = PS = 9 , PR is the perpendicular bisector of QS .

Therefore , QR ≅ RS by the Perpendicular Bisector Theorem.

So , QR = RS = 11.

QS=__________

Label the diagram with the information given in the question.

Since QR = RS = 66 , R  is equidistant from the endpoints of QS . Therefore R lies on the perpendicular bisector of QS by the Perpendicular Bisector Theorem.

Since R is on the perpendicular bisector of QS and ∠QTR is a right angle ,RT  is the perpendicular bisector of QS .

So, QT = ST = 42 and QS = 2. 42 = 84.

let’s practice!