Students, while in the computer lab, assess how to use Microsoft Excel as a "graphing calculator." They view visual representations of line graphs in a Cartesian plane while incorporating basic skills for using Excel productively.
Tenth graders explore parallel and perpendicular lines.  For this geometry lesson, 10th graders investigate the relationships associated with parallel lines and transversals, perpendicular lines, and the angles formed by these lines.  Cabri Jr. is required.
Here is a geometry lessonwhich invites learners to create models using their knowledge of lines, segments, rays, and angles. This lesson reinforces geometric vocabulary and concepts through practical application, it also includes extensions, list of terms, and an assessment.
Students investigate the relationship between perpendicular and parallel lines on a coordinate plane. In this geometry lesson, students differentiate lines based on their slopes.
In this geometry worksheet, students identify points, lines, planes, rays, segments and angles. They classify the intersection of geometric figures. This three-page worksheet contains examples, detailed instructions, and 12 problems. Answers are provided on the last page.
Young scholars write proofs for tangent and secant lines. In this geometry activity, students examine lines that are tangent and secant to a circle.
In this word search worksheet, learners locate words related to geometry. The word list includes vica versa, statement, given, hypothesis, and biconditional.
In this Algebra I/Algebra II/Geometry worksheet, students examine the slopes of parallel and perpendicular lines and the relationship to the equation of the line. The four page worksheet contains explanation of topic, worked examples, and four practice exercises. Answers to practice exercises are not provided. 
Students investigate congruent line segments. In this geometry lesson, students review parallel, intersecting and perpendicular lines. Students are then shown various shapes that have congruent lines. Students identify the line segments in the figure and the pairs of congruent lines. Students construct congruent line segments on paper.
Students investigate the centroid of a data set and its significance for the line fitted to the data. They investigate the relationship between a set of data points and a curve used to fit the data points.
Line of reflection is basically a geometry term used in the transformation of figures. It identifies the line on the graph that you reflect a figure over. The line can be vertical, horizontal, and diagonal. Actually, it can be any line on a graph that you use to get the mirror image of the given figure.
Skew lines? What? By definition, skew lines are lines on different planes that never intersect. Watch this video and get an explanation along with a visual diagram.
Mathematicians explore perpendicular, intersecting and parallel lines. In this geometry lesson, they view a map and identify the intersections. They also identify the parallel avenues on the map. This is a nice lesson that incorporates real-world applications.
While exploring the concept of transversals, Sal discusses corresponding angles, congruent angles, and opposite/vertical angles. He provides a thorough summation of these mathematical concepts. It is the first installment in a series covering parallel lines.
Students use an on-line worksheet to experiment with patterns of tessellations in regular polygons. As students observe different shapes in the "Tessellate" Activity they complete a data table and practice making predictions for different forms
In this diagnostic test learning exercise, students solve problems involving angles, parallel lines, and perpendicular lines. They identify alternate interior angles, alternate exterior angles, and corresponding angles. Students find the measurement of angles. This eight-page learning exercise contains 25 problems.
High schoolers investigate the shapes of nature using primary source images and compare the shapes to shapes in geometry. In this nature and geometry lesson plan, students compare different shapes and view a slideshow.
Students explore lines, rays, line segments, and planes. In this math lesson, students discuss the math concepts and direct their instructor in graphing functions. Students collaborate in graphing additional functions.
Students play with origami. In this geometry skills lesson, students use Internet sources to explore origami. Students apply geometry skills to create origami figures.
Third graders read "Pigs on the Ball" by Amy Axelrod and discuss the geometry concepts presented in the book. They use Twizzler sticks and pipe cleaners to represent lines, rays and angles.