Shmoop University
Shmoop: Basic Geometry: Area Formulas
The geometry resource investigates the area of polygons, triangles, circles, and squares. Formulas, examples, and practice exercises are included.
Shmoop University
Shmoop: Basic Geometry: Pythagorean Theorem
Students learn about the Pythagorean Theorem. Notes, practice problems, and examples are included in the geometry resource.
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: Problems Library Geometry Triangles
This site contains a wealth of problems that deal with the basic definitions of medians, altitudes, angle bisectors, and perpendicular bisectors or the defining characteristics of the different types of triangles. There are also...
Sophia Learning
Sophia: Triangle Proportionality Theorem: Lesson 4
This lesson presents how to apply the triangle proportionality theorem to solve for unknown variables and side lengths. It is 4 of 6 in the series titled "Triangle Proportionality Theorem."
Varsity Tutors
Varsity Tutors: Hotmath: Algebra Review: Types of Triangles
Find a quick, concise explanation of the different types of triangles. Examples are given and clearly explained.
Purple Math
Purplemath: Geometry Word Problems: Introduction
Introduces how to set up and solve simple geometric-figure word problems. Includes advice regarding formulas to memorize.
Mathigon
Mathigon: Geometry: Triangles and Trigonometry: Introduction
This lesson is an introduction to triangles and trigonometry by looking at the history of mapping and specifically, measuring the height of a mountain.
Ducksters
Ducksters: Kids Math: Triangles
Learn about equilateral, right angle, and isosceles triangles on this site. Learn how they work, terms, tricks and examples. .
Calculator Soup
Calculator Soup: Right Triangles Calculator
Use this calculator to find the unknown angles in a right triangle using the Pythagorean Theorem. Once you know the sides you can calculate the perimeter, semiperimeter, area, and the altitudes.
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: Triangle Theorems Calculator
Each calculation option has sub-bullets that list the sequence of methods used in this calculator to solve for unknown angle and side values including Sum of Angles in a Triangle, Law of Sines, and Law of Cosines.
Wolfram Research
Wolfram Math World: Scalene Triangles
MathWorld gives a brief definition of scalene triangles and then lists links to related topics and terms.
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.