Unit Plan
Shmoop University

Shmoop: Basic Geometry: Area Formulas

For Students 9th - 10th Standards
The geometry resource investigates the area of polygons, triangles, circles, and squares. Formulas, examples, and practice exercises are included.
Unit Plan
Shmoop University

Shmoop: Basic Geometry: Pythagorean Theorem

For Students 9th - 10th Standards
Students learn about the Pythagorean Theorem. Notes, practice problems, and examples are included in the geometry resource.
Website
National Council of Teachers of Mathematics

The Math Forum: Ask Dr. Math: Triangle Altitudes

For Students 9th - 10th Standards
Here at the Math Forum, Dr. Math proves the concurrency of the altitudes of a triangle. Links are provided for associated topics.
Activity
National Council of Teachers of Mathematics

The Math Forum: Problems Library Geometry Triangles

For Students 9th - 10th Standards
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...
PPT
Sophia Learning

Sophia: Triangle Proportionality Theorem: Lesson 4

For Students 9th - 10th Standards
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."
Handout
Varsity Tutors

Varsity Tutors: Hotmath: Algebra Review: Types of Triangles

For Students 9th - 10th Standards
Find a quick, concise explanation of the different types of triangles. Examples are given and clearly explained.
Handout
Purple Math

Purplemath: Geometry Word Problems: Introduction

For Students 9th - 10th Standards
Introduces how to set up and solve simple geometric-figure word problems. Includes advice regarding formulas to memorize.
eBook
Mathigon

Mathigon: Geometry: Triangles and Trigonometry: Introduction

For Students 9th - 10th Standards
This lesson is an introduction to triangles and trigonometry by looking at the history of mapping and specifically, measuring the height of a mountain.
Website
Ducksters

Ducksters: Kids Math: Triangles

For Students 1st - 9th Standards
Learn about equilateral, right angle, and isosceles triangles on this site. Learn how they work, terms, tricks and examples. .
Interactive
Calculator Soup

Calculator Soup: Right Triangles Calculator

For Students 9th - 10th Standards
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.
Handout
Calculator Soup

Calculator Soup: Isosceles Triangles Calculator

For Students 9th - 10th Standards
Use this calculator to find the sides, perimeter, area, semiperimeter, and altitude of an isosceles triangle.
Interactive
Calculator Soup

Calculator Soup: Triangle Theorems Calculator

For Students 9th - 10th Standards
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.
Handout
Wolfram Research

Wolfram Math World: Scalene Triangles

For Students 9th - 10th Standards
MathWorld gives a brief definition of scalene triangles and then lists links to related topics and terms.
Handout
Wolfram Research

Wolfram Math World: Circumcenter

For Students 9th - 10th Standards
MathWorld diagrams a triangle with its circumcenter labeled and details how to find the circumcenter with links to the key terms.
Lesson Plan
Science and Mathematics Initiative for Learning Enhancement (SMILE)

Smile: Geometry Distance of Triangles Using a Protractor

For Teachers 5th - 9th Standards
Basic exercises are presented to help students understand the concept of the area of triangles and the angles of a triangle.