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.
Illustrative Mathematics
Illustrative Mathematics: 8.g Congruence of Alternate Interior Angles
Eighth graders are presented with a labeled drawing of two parallel lines intersected by a transversal line. They are asked to discuss congruency of angles when the picture is rotated about a point on the transversal. Aligns with 8.G.A.5.
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.
Illustrative Mathematics
Illustrative Mathematics: 8.g Find the Missing Angle
In this task, 8th graders are presented with a drawing of two parallel lines connected through two line segments. They are given the measures of two angles and are asked to find a third. Aligns with 8.G.A.5.
Math Open Reference
Math Open Reference: Corresponding Angles
Learn about corresponding angles with this resource which offers detailed explanations and examples. Subjects covered include parallel and non-parallel cases. Links to related topics.
Math Open Reference
Math Open Reference: Alternate Interior Angles
Explore the triangle inequality theorem with this helpful reference tool. Provides a detailed definition and an interactive activity that enhances further explanation. Includes links to related topics.
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.