This study guide on lines in a coordinate plane covers key terms, what different line slopes look like, postulates about parallel and perpendicular lines, the slope-intercept equation, how to graph parallel and perpendicular lines, and...

Explains the basic concept of perpendicular lines with step-by-step instructions and methods for solving specific problems on your own relating to this topic.

Alex and his friends are studying for a geometry test and one of the main topics covered is parallel lines. They each write down what they think it means for two distinct lines in a plane to be parallel. Students are asked to analyze...

Construct a copy of a line segment in this interactive exercise.

Consider two parallel lines that are intersected by a transversal, and when it crosses the two others, many different angle pairs are formed. See the special properties of the angle pairs in this interactive.

Learn the four categories of theorems that have to do with lines and angles.

[Free Registration/Login may be required to access all resource tools.] Determine the formula for finding the coordinates of a point on a line segment.

This fourth-grade geometry lesson teaches the definitions for a line, ray, angle, acute angle, right angle, and obtuse angle. We also study how the size of the angle is ONLY determined by how much it has "opened" as compared to the whole...

Use this site for two short lesson plans regarding Euclidean and Spherical lines. Intersecting and parallel lines are discussed. The lesson contains activities for two days of class.

Reflect any point, line segment, triangle, or any other figure over one or two lines using this dynamic applet. Points and lines are entered by point-and-click rather than by typing equations or ordered pairs. A very neat exercise to...

Explore the world of transversals in this mini-lesson. Learn about transversals, transversal lines, and angles. There are transversal examples and a few interesting practice questions at the end of the page to strengthen your concepts of...

Here is a partial list of theorems, postulates, and properties.

This site from Advogato is all about angles. It contains information starting with what an angle is and what it looks like, all the way up to bisecting angles and theorems about angles. This is very good information for students just...

A "convention" is "just the way a thing is done!". This reference material lists some common conventions (notational assumptions) for geometry and trigonometry.

In this task, young scholars are shown three unit squares and two line segments connecting two pairs of vertices. They are asked to find the area of a triangle formed by intersecting lines. They can solve it using coordinate geometry or...

This task uses GeoGebra software, which can be freely downloaded, to explore what happens to the line segments and angles of a triangle when it is reflected, rotated, and translated. Includes printable task sheet for students and a...

Scroll down to find a definition of horizontal with hyperlinks to other definitions on the site.

Provides a definition and examples of perpendicular bisectors.

For this task, students are shown a unit circle in a plane and an angle measured from the x-axis. They must determine the coordinates of the line segment for the angle and answer a question about the sum of the coordinates. The purpose...

This site offers numerous activities for middle school and high school students to explore using Geometer's Sketch Pad.

Learn about intersections with this helpful reference tool. Provides a detailed definition and an interactive activity that enhance further explanation. Includes links to related topics.