Geometry: Finding the Coordinates of an Endpoint

Objectives:

• Students will review finding the coordinates of a midpoint.

• Students will learn to use the midpoint formula to find the coordinates of an unknown endpoint.

• Students will graph the line segments on the coordinate plane.

• Students will practice these skills in their independent work.

Suggested Grades:

Seventh Grade - Eighth Grade - Ninth Grade - Tenth Grade - including Special Education students

Lesson Procedure:

Print the classroom lesson plan and worksheet questions (see below).

Lesson Excerpt:

Finding the Endpoint of a Line

When we find the endpoint of a line, we are going be working backwards in a way. We are going to be given the coordinates of the midpoint and one of the endpoints. Then we will use the midpoint formula and our given information to find the coordinates of the unknown endpoint. Finally, we can graph our findings.

Let’s start with an example and work through this.

CE has a midpoint of D.
The coordinates of point C are (6,2)
The coordinates of the midpoint D are (4,3).
Find the coordinates of endpoint E.

To work through this problem, let’s begin by substituting what we know into the midpoint formula.

Continued...