Khan Academy
Khan Academy: Find Missing Length When Given Area of a Triangle
Find the base or height of a triangle when given the other and the area. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.
CK-12 Foundation
Ck 12: Elem Math: Identifying Rectangles Squares Circles and Triangles
[Free Registration/Login may be required to access all resource tools.] The video briefly shows and describes a triangle, circle, rectangle, and square and uses process of elimination to determine the given shape. The video is followed...
CK-12 Foundation
Ck 12: Triangle Identification as Similar, Congruent, or Neither
[Free Registration/Login may be required to access all resource tools.] Determine whether triangles are similar, congruent, or neither.
Other
Transition Mathematics: Polygons
This site has an extensive definition of a polygon. The definition is followed by multiple-choice questions that ask the student to name specific polygons. There is a link for more questions about polygons.
Merriam-Webster
Merriam Webster: Dictionary Illustration: Incenter
A labeled illustration of an incenter inside a triangle.
National Council of Teachers of Mathematics
The Math Forum: Building Shapes
Based on building a hexagon, this activity from the Math Forum collection focuses on using different combinations of pattern blocks to create a hexagon. An online activity, pencil and paper method, literature connections, and a...
National Council of Teachers of Mathematics
The Math Forum: Line Symmetry
This site from The Math Forum is a great site if you are looking for activities to engage your students in learning about line symmetry. Peruse this collection of activities for one or two or four that would be right for your students....
Texas Instruments
Texas Instruments: Similar Triangles and Proportions
In this activity, students will investigate the relationship among the similar triangles formed when a segment is constructed parallel to one side of a triangle. They will explore the various ratios that exist between the lengths of the...
Texas Instruments
Texas Instruments: Triangle Proportionality
In this activity, students will study the concept of triangle proportionality. [Requires Adobe Reader.]
Texas Instruments
Texas Instruments: Investigating Segments in a Triangle
In this activity, students investigate the midsegments of a triangle as in the previous activity. They continue to explore these segments and extend their understanding of the relationships that exist between the slopes of lines...
Texas Instruments
Texas Instruments: Triangle Properties Assessment
This activity uses Cabri Jr. to assess the students' knowledge of various segments related to triangles: perpendicular bisector, median, angle bisector, midsegment, and altitude.
Texas Instruments
Texas Instruments: Investigating the Triangle Inequality
One property of a triangle is that the sum of the lengths of any two sides must be greater than the length of the third side. [Requires Adobe Reader.]
Texas Instruments
Texas Instruments: Triangle Inequalities
This activity will help students visualize the properties of triangles stated in the theorems. By dragging the vertices, the students can see that the properties hold regardless of the size of the triangles and which sides are the...
Harvard University
University of Harvard: This Is a Stickup!
Students are taught how to make a sundial. The relationship between angles and the sides of a right triangle are explored. Great lesson plan ideas with plenty of background information. The lesson is adapted for grade levels k-6 with...
Purple Math
Purplemath: Basic Triangle Values
This Purplemath lesson explains a simple pictorial way to remember basic reference angle values.
Northeast Parallel Architectures Center, Syracuse University
Npac Reu Program: Graphing With Coordinates in the Plane
This site from the Northeast Parallel Architectures Center, Syracuse University provides a good five-part basic graphing instructor. Covers all the basics clearly. It is divided into links for easier navigation.
Depaul University
Depaul University: Inscribing Regular Polygons
In this lesson, students learn to inscribe regular polygons inside a circle.
CK-12 Foundation
Ck 12: Area and Perimeter of Triangles
[Free Registration/Login Required] Students are given the base and height of a triangle and are to determine the area and perimeter. Click challenge me to answer practice questions and click learn more to watch a video.
CK-12 Foundation
Ck 12: Geometry: Area and Perimeter of Triangles
[Free Registration/Login may be required to access all resource tools.] In this lesson students calculate the area and perimeter of a triangle. Students examine guided notes, review guided practice, watch instructional videos and attempt...
CK-12 Foundation
Ck 12: Geometry: Area and Perimeter of Triangles
[Free Registration/Login may be required to access all resource tools.] This concept teaches students to find the area and perimeter of triangles. Students examine guided notes, review guided practice, watch instructional videos and...
Oswego City School District
Regents Exam Prep Center: Triangle Information
This Oswego City School District site from the Regents Exam Prep Center provides an explanation of the classifications of triangles both by sides and by angles. Pictures are also included.
Oswego City School District
Regents Exam Prep Center: Congruence of Triangles
Congruent means, "same size, same shape." Find out more about this concept at this test prep site with real world examples and pictures. Hands-on classroom activity and lots of practice. Knowledge of basic algebra and geometry concepts...
Oswego City School District
Regents Exam Prep Center: Pythagorean Theorem
Who was Pythagoras and what is his theorem? Explore this concept and its relationship to the measurement of a right triangle in this test prep lesson plan. The instructional activity includes an interactive worksheet where middle...
University of California
University of California: Triangles and Simplices
This site from the University of California deals with different applications and topics pertaining to triangles, particularly triangulation.