Geometry Help
Geometry Help: Lines and Angles
Explains the basic concept of lines and angles with step-by-step instructions and methods for solving specific problems on your own relating to this topic.
City University of New York
Lehman College: An Introduction to Lines
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.
CK-12 Foundation
Ck 12: Interactive Geometry: 4.2 Theorems About Lines and Angles
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.
Purple Math
Purplemath: Conventions
A "convention" is "just the way a thing is done!". This reference material lists some common conventions (notational assumptions) for geometry and trigonometry.
Illustrative Mathematics
Illustrative Mathematics: G Gpe, G Co, G Srt Unit Squares and Triangles
In this task, students 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...
Oswego City School District
Regents Exam Prep Center: Geometric Constructions
Learn all about the basic geometric constructions in this test prep lesson. You will explore line segments and points, and understand key terms like the terms parallel and perpendicular. Construction activities and interactive online...