CK-12 Foundation
Ck 12: Geometry: Altitudes
[Free Registration/Login may be required to access all resource tools.] Apply the properties of altitudes.
Wolfram Research
Wolfram Mathworld: Isosceles Triangle
MathWorld explains what an isosceles triangle is and how it compares with equilateral, and scalene triangles. The altitude and area of these triangles are also discussed.
CK-12 Foundation
Ck 12: Geometry: Inscribed Similar Triangles
[Free Registration/Login may be required to access all resource tools.] Apply the fact that the altitude of a right triangle creates similar triangles.
CK-12 Foundation
Ck 12: Geometry: Right Triangle Similarity Study Guide
[Free Registration/Login may be required to access all resource tools.] An overview of altitudes and geometric mean is provided in this study guide.
Math Planet
Math Planet: Geometry: More About Triangles
Explores triangles and related vocabulary through examples and a video lesson.
Duke University
Duke University: Web Feats Ii: Altitude Theorem for Equilateral Triangles
This resource provides information about the altitude theorem for equilateral triangles, in addition to links on related topics. Requires Java.
Government of Alberta
Learn alberta.ca: Mathematics Glossary: Altitude(s) of a Triangle
Get a visual and animated definition of the altitude(s) of a triangle from LearnAlberta.ca's Mathematics Glossary. [Requires Java.]
Math Open Reference
Math Open Reference: Altitude of a Triangle
Learn about the altitude of a triangle with this handy reference tool. Provides a detailed definition, examples, and an interactive activity that enhances further explanation. Includes links to related topics.
Wolfram Research
Wolfram Math World: Equilateral Triangle
MathWorld goes into detail about equilateral triangles at this site. Use this site to find out how to construct an equilateral triangle using a compass and straight edge. Learn about the altitude of such triangles, and the rationality of...
Homeschool Math
Homeschool Math: Area of Triangles
This lesson presents the idea that the area of any triangle is exactly half of a certain parallelogram -- thus we get the familiar formula of multiplying the base and the altitude and taking half of that. The lesson contains varied...
CK-12 Foundation
Ck 12: Altitudes: Orthocenter
[Free Registration/Login Required] Students will use the interactive riangle and points to explore altitudes such as the orthocenter. Click learn more to watch a video and click challenge me to answer a practice question.
Texas Instruments
Texas Instruments: Exploring the Orthocenter of a Triangle
In this activity, students use the Cabri Jr. tools to draw altitudes in a triangle. They construct a line perpendicular to a given line and through a given point. [Requires Adobe Reader.]
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.
Wolfram Research
Wolfram Math World: Altitude
This site from Math World describes the altitude of a triangle, and shows how to find these altitudes using the parameter and positions of the vertexes and angles of the triangle. The site gives other interesting formulas involving the...
Homeschool Math
Homeschool Math: How to Construct an Altitude to a Triangle
Exercises explain how to construct an altitude to a triangle.
Sophia Learning
Sophia: Triangle Height: Lesson 2
This lesson will demonstrate how to locate the height in an obtuse, right, and acute triangle. It is 2 of 5 in the series titled "Triangle Height."
Sophia Learning
Sophia: Triangle Height: Lesson 4
This lesson will demonstrate how to locate the height in an obtuse, right, and acute triangle. It is 4 of 5 in the series titled "Triangle Height."
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.
University of Georgia
University of Georgia: Inter Math: Altitude of a Triangle
This site gives a description along with a visual representation of the altitude of a triangle. There are links to related terms, everyday examples, challenging problems, more information, and the interactive check point involving...
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...
Texas Instruments
Texas Instruments: The Orthocenter of a Triangle
Students understand that the orthocenter is the point of concurrence of the three altitudes of a triangle. They construct circumcircles and Feuerbach circles and determine the relationship between them.
Math Open Reference
Math Open Reference: Orthocenter of a Triangle
Learn about the orthocenter of a triangle with this handy reference guide. Provides a detailed definition, examples, and an interactive activity that enhances further explanation. Includes links to related topics.
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.
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.