A location of a line on the coordinate plane is defined by two or more points whose coordinates are known. The line passes through both points and goes on forever in both directions. It has no endpoints.

This is the same as the definition of a line in ordinary plane geometry, the only difference being that we know the coordinates of the points involved. The naming conventions are also the same.

Things to try

1. In the above diagram, press 'Reset'. The line AB passes through point A at (52,7), point B at (53,20) and goes to infinity in both directions.
2. Drag A, B or the origin point and construct various other lines to get a feel for the concept.

See also the Definition of a Line in plane geometry.

Other Coordinate Geometry entries

• Introduction to coordinate geometry
• The coordinate plane
• Coordinates of a point
• Distance between two points

• Introduction to Lines in Coordinate Geometry
• Lines (in Coordinate Geometry)
• Rays (in Coordinate Geometry)
• Line Segments (in Coordinate Geometry)
• Midpoint of a line segment (Midpoint Theorem)

• Distance from a point to a line - introduction
• - When line is horizontal or vertical
• - Using two line equations
• - Using trigonometry
• - Using a formula

• Slope (m) of a line
• Intercept (b) of a line
• Equation of a line in slope-intercept form y=mx+b
• Equation of a line in point-slope form y=m(x-Px)+Py

• Vertical lines
• Horizontal lines
• Parallel lines
• Perpendicular lines
• Intersecting lines

• Cirumscribed rectangle (bounding box)
• Area of a triangle (formula method)
• Area of a triangle (box method)
• Area of a polygon
• Area of a polygon (calculator)
• Rectangle
• Definition and properties, diagonals
• Area and perimeter
• Square
• Definition and properties, diagonals
• Area and perimeter
• Trapezoid
• Definition and properties, altitude, median
• Area and perimeter
• Parallelogram
• Definition and properties, altitude, diagonals

• Print blank graph paper