Ministry of Education and Employment of Spain
Red Escolar: Un Triangulo Sorprendente
In Spanish. Different activities which involve the following concepts: right triangles, perpendicular lines, classification of triangles, area of a square and Pythagorean theorem.
AAA Math
Aaa Math: Finding the Third Angle of a Triangle
Finding the third angle of a triangle becomes easier by the explanation and examples presented.
University of Georgia
University of Georgia: Altitudes & Orthocenters: Making Connections
This site describes altitudes and orthocenters in triangles and their connections with the nine-point circle.
Wolfram Research
Wolfram Math World: Orthocenter
This site from MathWorld provides a diagram of a triangle with its orthocenter labeled. The site details how to find the orthocenter with links to the key terms. The site details many other interesting properties of the triangle...
ClassFlow
Class Flow: Right Triangles
[Free Registration/Login Required] Use this flipchart to help your high school students understand right triangles using the Pythagorean Theorem.
ClassFlow
Class Flow: Triangle Segments
[Free Registration/Login Required] In this flipchart, students use the interactive features of Activstudio to understand how to use the properties of perpendicular bisectors, angle bisectors, medians and altitudes of a triangle.
Free Math Help
Free Math Help: Isosceles Triangles
Students learn about isosceles triangles. The tutorial consists of definitions and sample exercises with solutions.
Free Math Help
Free Math Help: Area Formulas
The resource consists of area formulas and diagrams for a square, rectangle, circle, triangle, and trapezoid.
Shmoop University
Shmoop: Basic Geometry: Triangles
The geometry resource explores triangles. Descriptions, examples, and practice exercises are included.
National Council of Teachers of Mathematics
The Math Forum: Ask Dr. Math: Triangle Altitudes
Here at the Math Forum, Dr. Math proves the concurrency of the altitudes of a triangle. Links are provided for associated topics.
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.
National Council of Teachers of Mathematics
Nctm: Illuminations: Triangle Classification
Use this applet to show how the placement of the third vertex of a triangle affects the classification of that triangle.
Calculator Soup
Calculator Soup: Isosceles Triangles Calculator
Use this calculator to find the sides, perimeter, area, semiperimeter, and altitude of an isosceles triangle.
Calculator Soup
Calculator Soup: Equilateral Triangles Calculator
An equilateral triangle is a special case of a triangle where all 3 sides have equal length and all 3 angles are equal to 60 degrees.
Wolfram Research
Wolfram Math World: Circumcenter
MathWorld diagrams a triangle with its circumcenter labeled and details how to find the circumcenter with links to the key terms.
Science and Mathematics Initiative for Learning Enhancement (SMILE)
Smile: Geometry Distance of Triangles Using a Protractor
Basic exercises are presented to help students understand the concept of the area of triangles and the angles of a triangle.