Use the distance formula to prove geometric properties and find equidistant points.
Preview · progress not saved — Chapter 1 is free
Table mapping geometric conditions to coordinate geometry distance checks.
Worked example showing how to prove points form a square.
Problem. Show that the points , , and are the vertices of a square.
Fig 7.6 showing students seated in a classroom.
photorealistic educational scene, shot on 35mm lens, natural lighting with soft bokeh, warm inviting color grading, gold…
Proving Ashima, Bharti, and Camella are seated in a line.
To prove points A(3, 1), B(6, 4), and C(8, 6) are collinear, we must find the distances between them. Distance AB is calculated as and BC is calculated as . The total distance AC is , which evaluates to . Factoring out a perfect square, simplifies to . When we add AB and BC, we get . This technique of verifying distance sums is a core tool in coordinate geometry. Because the sum of the two shorter distances exactly equals the longest distance , we can conclude the three students are seated in a straight .
Setting up equations for points at equal distances.
When a point is equidistant from two other points and , it means the distance from to is exactly the same as the distance from to .
Geometrically, this means lies somewhere on the perpendicular bisector of the line segment joining and .
Worked example finding relation between x and y for an equidistant point.
Problem. Find a relation between and such that the point is equidistant from the points and .
Worked example finding a specific point on the y-axis.
Problem. Find a point on the y-axis which is equidistant from the points and .