Mathematics Grade 10 15 min

Perpendicular Bisector Theorem

Perpendicular Bisector Theorem

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Introduction & Learning Objectives

Learning Objectives Define a perpendicular bisector and its properties. State and explain the Perpendicular Bisector Theorem. State and explain the Converse of the Perpendicular Bisector Theorem. Apply the theorem and its converse to solve for unknown lengths and variables in geometric figures. Prove the Perpendicular Bisector Theorem using triangle congruence postulates. Determine if a point lies on a perpendicular bisector by applying the converse of the theorem. Imagine you and a friend are standing in a field. Where could a third person stand so they are the exact same distance from both of you? 🤔 This tutorial explores the Perpendicular Bisector Theorem, a fundamental rule in geometry that connects points, distances, and lines. You will learn the theorem, its converse...
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Key Concepts & Vocabulary

TermDefinitionExample Perpendicular BisectorA line, ray, or segment that intersects another segment at its midpoint and forms a 90° angle.If line 'l' passes through the midpoint M of segment AB and l ⊥ AB, then 'l' is the perpendicular bisector of AB. EquidistantBeing at an equal distance from two or more points.If the distance from point C to point A is 5 cm, and the distance from point C to point B is also 5 cm, then C is equidistant from A and B. MidpointThe point on a line segment that divides it into two congruent (equal length) segments.If M is the midpoint of segment XY, then XM = MY. Perpendicular LinesTwo lines that intersect to form a right angle (90°).The x-axis and y-axis on a Cartesian plane are perpendicular lines. Congruent SegmentsLine segments that hav...
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Core Formulas

Perpendicular Bisector Theorem If a point lies on the perpendicular bisector of a segment, then it is equidistant from the endpoints of the segment. Use this theorem when you are GIVEN that a line is a perpendicular bisector and you need to prove or find the lengths of the segments connecting a point on that line to the endpoints. If line 'l' is the perpendicular bisector of segment AB and point P is on 'l', then PA = PB. Converse of the Perpendicular Bisector Theorem If a point is equidistant from the endpoints of a segment, then it lies on the perpendicular bisector of the segment. Use this theorem when you are GIVEN that a point is equidistant from a segment's endpoints and you need to prove that the point lies on the perpendicular bisector. If PA...

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Sample Practice Questions

Challenging
What is the equation of the perpendicular bisector of the segment with endpoints A(-2, 1) and B(4, 5)?
A.y = -3/2x + 9/2
B.y = 2/3x + 7/3
C.y = -3/2x + 3
D.y = 2/3x + 3
Challenging
In isosceles triangle ΔXYZ with base YZ, the altitude from vertex X to the base is drawn, meeting the base at M. Why is this altitude XM guaranteed to be the perpendicular bisector of YZ?
A.By definition, an altitude is always a perpendicular bisector.
B.Because ΔXYZ is isosceles, XY = XZ, making point X equidistant from Y and Z. The Converse of the Perpendicular Bisector Theorem applies.
C.The Perpendicular Bisector Theorem states that any line from a vertex to the opposite side is a perpendicular bisector.
D.This can only be proven using the Pythagorean theorem.
Challenging
In ΔABC, the perpendicular bisector of side AB and the perpendicular bisector of side BC intersect at a point P. Which of the following statements must be true?
A.P is the midpoint of AC.
B.PA = PB and PB = PC, therefore PA = PC.
C.Triangle ABC must be a right triangle.
D.Point P lies on side AC.

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