National Council of Teachers of Mathematics
The Math Forum: Triangle Formulas
Investigate the geometric definitions of triangles, focusing upon equilateral, isosceles, right, and scalene with detailed drawings and appropriate formulas for each. This site has links to more information on triangles.
Math Is Fun
Math Is Fun: Constructing a Triangle With 3 Known Sides
Students learn how to construct a triangle with three known sides using a straightedge and a compass. Includes an animated demonstration.
Khan Academy
Khan Academy: Constructing Triangles
Given the lengths of two sides of a triangle, what can we say about the third side? Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.
Government of Alberta
Learn Alberta: Math Interactives: Exploring Square Roots Video
This video illustrates the concepts of square roots, slope, and the Pythagorean Theorem as they are used in designing and constructing skate park rails, ramps, and pipes. An interactive activity is also included where students are able...
Texas Instruments
Texas Instruments: Investigate Triangles and Congruence
Students can use the TI-84 Plus family with Cabri Jr. to prove triangle congruence with SSA.
Maths Challenge
Maths challenge.net: Perpendicular Construction
This is a "three star" geometry problem where prior math problem skills and proof experience is recommended to solve this "Perpendicular Construction" problem.
Math Open Reference
Math Open Reference: Constructions
Learn about drawing shapes using only a compass and straight edge or ruler with out measuring any lengths or angles.
Khan Academy
Khan Academy: Triangle Side Length Rules
Practice solving problems with triangle side length rules.
Oswego City School District
Regents Exam Prep Center: Reference Angles and Triangles
The mathematics session investigates reference angles and triangles. The tutorial consists of class notes, examples, and practice problems with solutions. The teacher resource includes a worksheet on the construction of skateboarding ramps.
National Council of Teachers of Mathematics
The Math Forum: Ask Dr. Math: Constructing the Orthocenter
Dr. Math shows how to construct the orthocenter of any triangle using a compass and straight edge.
Wolfram Research
Wolfram Math World: Right Triangle
This site from MathWorld.com offers extensive information on right triangles. The site contains information on numerous characteristics of right triangles, including constructing similar inscribed triangles, altitudes, Pythagorean...
Math Is Fun
Math Is Fun: Using a Ruler and Drafting Triangle
Students learn how to construct parallel and perpendicular lines. The resource consists of video demonstrations.
University of Cambridge
University of Cambridge: Nrich: Seven Sticks
On this one page website sharpen your logic, triangle properties, and pattern recognition skills while working on this challenge. The solution is available to double check your solution.