Curated OER
Tangent Lines and the Radius of a Circle
Your Geometry learners will collaboratively prove that the tangent line of a circle is perpendicular to the radius of the circle. A deliberately sparse introduction allows for a variety of approaches to find a solution.
Illustrative Mathematics
Slopes and Circles
An upper-level treatment of what is often presented as a basic concept (the right angle of an inscribed circle on the diameter), this activity really elevates the mathematical thought of the learner! Expected to develop formulas...
Illustrative Mathematics
The Geometry of Letters
Use the alphabet as a tool for teaching your class about geometric figures. Break apart capital letters into line segments and arcs. Classify angles as right, acute, or obtuse. Identify parallel and perpendicular lines. An excellent...
Illustrative Mathematics
Hexagonal Pattern of Beehives
Young geometers and biologists investigate the math of nature in an activity that is just the bee's knees. Participants will study the tessellations of hexagons in a beehive, along with the natural rationale behind the specific shape....
Varsity Tutors
Varsity Tutors: Hotmath: Practice Problems: Geometry in the Plane
Twenty-four problems presented on a variety of Plane Geometry topics. They are given with each step to the solution cleverly revealed one at a time. You can work each step of the problem then click the "View Solution" button to check...
University of Saskatchewan (Canada)
University of Saskatchewan: Geometry
The University of Saskatchewan's Department of Mathematics and Statistics provides high school students with online tutorials and exercises on what they deem some of the most important topics in geometry: Triangles, and Circles and Other...
CK-12 Foundation
Ck 12: Circles in the Coordinate Plane
[Free Registration/Login Required] Students will move points on a circle to explore standard equations when given the radius and center. Click challenge me to answer practice problems and click learn more to watch a video.
CK-12 Foundation
Ck 12: Circles in the Coordinate Plane: Watering the Field
[Free Registration/Login Required] Students can move points in a circle to determine the standard equation from the raidus and center. Click challenge me to answer practice questions and click learn more to watch a video.
National Council of Teachers of Mathematics
The Math Forum: Analytic Geometry: Polar Coordinates
This site from The Math Forum provides great information on polar coordinates. You can access this information either by clicking on the coordinates link or just scrolling down, it is the first one listed on the page. Includes several...
University of Cambridge
University of Cambridge: Maths and Sports: Sports Equipment
Sports such as hockey, football, basketball and tennis use balls of different sizes. Can you arrange a selection of different balls in a line each touching the next to make the shortest line? This activity offers opportunities for...
Scholastic
Scholastic: Max's Math Adventures: Max's Fantastical Zoo
Use this rhyming description of Max's Fantastical Zoo to make some amazing animals from geometric shapes. There is a teacher's guide for easy lesson planning.
NumberNut
Number Nut: Shapes, Symbols, and Colors: 2 D Shapes
Did you know that two-dimensional shapes are also called polygons? This lesson describes the various 2-D shapes and includes two interactive games to reinforce skills.