Texas Instruments
Texas Instruments: Triangle Proportionality
In this activity, students will study the concept of triangle proportionality. [Requires Adobe Reader.]
Harvard University
University of Harvard: This Is a Stickup!
Learners 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.
CK-12 Foundation
Ck 12: Pythagorean Triples
[Free Registration/Login Required] Students explore the concept of pythagorean triples by navigating through the interactive learning module and then answering questions that go along with the module. Students can also learn more about...
CK-12 Foundation
Ck 12: Triangle Classification
[Free Registration/Login Required] Students will move the vertices to different points to create different obtuse triangles. Click learn more to watch a video demonstration and click challenge me to answer a practice question.
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.
Khan Academy
Khan Academy: Find Angles in Isosceles Triangles
Find missing angles in isosceles triangles given just one angle. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.
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...
Analyze Math
Analyze Math: Area of Triangles
The geometry resource explores the different formulas used to calculate the area of triangles. The applet investigates the angles and sides of a triangle.
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.
Science Struck
Science Struck: List of Different Types of Geometric Shapes
A comprehensive list of 2D shapes and 3D solids with everything from a triangle to a dodecahedron. Includes illustrations and short descriptions of attributes for each.
Math Planet
Math Planet: Pre Algebra: Triangles
Learn about the types of triangles by taking a look at an example and a video lesson.
Khan Academy
Khan Academy: Dilate Triangles
Given a figure and a definition of a dilation, draw the image. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.
Math Warehouse
Math Warehouse: Pythagorean Theorem
Resource takes a look at how to use the Pythagorean Theorem. Includes formulas, examples, animations, and practice problems.
BBC
Bbc: Pythagoras' Theorem
You can pick up some valuable pointers on how to apply the Pythagorean Theorem here. When you finish working your way through the pages you can take an on-line "Test Bite," and check your understanding.
Illustrative Mathematics
Illustrative Mathematics: G Co, G Srt Seven Circles I
In this task, seven pennies are placed in a circle so that they are all touching one in the center and their neighbors. The question is whether this will work with other equally-sized circles. Aligns with G-SRT.C and G-CO.C.10.