Curated OER
Ratios in Right Triangles
Learners calculate the sides of right triangles in this trigonometric ratios lesson. They use Cabri Jr. software and TI-83 or TI-84 calculators to find the side lengths and their ratios to each other for various triangles. The provided...
Maths Challenge
Maths challenge.net: Right Triangle Equal Parts
A geometry proof problem involving a right triangle and finding angles of equal measure.
Varsity Tutors
Varsity Tutors: Hotmath: Practice Problems: Right Triangles and Trigonometry
Twenty-five problems cover the topic of right triangles and trigonometry in different settings. They are given with each step to the solution cleverly revealed one at a time. You can work each step of the problem then click the "View...
TeachEngineering
Teach Engineering: Handheld Trigonometry
In addition to understanding the concept of similar right triangles and how they apply to trigonometric ratios, students explore a clinometer app, and discover how it can be used to test the mathematics underpinning trigonometry.
That Quiz
That Quiz: Practice Test: Triangles
Test your knowledge on the attributes of triangles. There are eleven levels that may be completed with or without a timer.
University of Georgia
University of Georgia: An Elementary Application of Similar Triangles
Excellent review site on similar triangles. Includes diagrams and explanation of application.
Oswego City School District
Regents Exam Prep Center: Angles and Triangles
On this site a viewer can learn about the different types of triangles, and categorized by either angles or sides. Tutorials are also included for interior and exterior angles of triangles. A teacher resource page includes a lesson plan...
Mathigon
Mathigon: Geometry: Triangles and Trigonometry: Properties of Triangles
This lesson focuses on the properties of triangles, a closed shape that has three sides, three vertices, and and three internal angles. There are different types of triangles such as a right triangle, obtuse, and acute based on the...
Cuemath
Cuemath: Right Angled Triangle
Explore and learn about the features and properties of a right triangle in this lesson. Includes examples and practice questions.
Cuemath
Cuemath: Obtuse Triangle
In this mini-lesson, learn about obtuse triangles including the obtuse triangle definition, sides, properties, examples, and other fun facts related to it.
Cuemath
Cuemath: Acute Triangle
Explore the world of acute triangles in this mini-lesson. Explores its properties, how to create it, and other interesting facts related to acute triangles.
Curated OER
Zona Land: Right Triangle Solver 3
A java applet that will solve a right triangle when you provide angle D and the length of the hypotenuse f.
Wolfram Research
Wolfram Math World: Law of Cosines
This page from MathWorld.com gives a good explanation of the Law of Cosines, which relates the lengths of the legs of a triangle to the angles. This site shows how the formula is derived, along with a triangle to clarify variables. Also...
Wolfram Research
Wolfram Math World: Obtuse Triangles
MathWorld.com offers information on obtuse triangles and links to related terms and formulas.
Wolfram Research
Wolfram Math World: Acute Triangle
This MathWorld site gives a short discussion on acute triangles with links to related terms and topics. The site offers a discussion on the least number of acute triangles to compose various polygons, and a discussion on the relationship...
Texas Instruments
Texas Instruments: Constructing Triangles
This activity focuses on the various ways to construct the different types of triangles such as isosceles, equilateral, right, and right isosceles triangles. Students will begin by constructing triangles based on a minimal definition of...
Texas Instruments
Texas Instruments: Math Today When a Ruler Isn't Enough
This activity illustrates a real-life problem that uses trigonometry to solve for an unknown. students can use trigonometric ratios and inverse trigonometric relationships to determine the side of a triangle and the measure of the...
Texas Instruments
Texas Instruments: Investigating Segments in a Right Triangle
In this activity, students review definitions of terms such as right triangle, hypotenuse, midpoint, vertices, and equidistant. They also discover an important characteristic of the midpoint of the hypotenuse.
Texas Instruments
Texas Instruments: Sin, Cos, and Tan of Right Triangles
In this activity, students explore a right angled triangle and its trigonometric concepts. They investigate the trigonometric ratios for the angles of the triangle.
Texas Instruments
Texas Instruments: Looking for Mr. Right Triangle
Navigator Activity: This is a review of the right triangle in the coordinate plane. Given two lines (2 really nice ones) the students write the equation of the 3rd line to create a right triangle. They find the vertices of the triangle...
Texas Instruments
Texas Instruments: Ratios in Right Triangles
The study of properties of right triangles is a major topic in mathematics. In this activity, you will investigate three common right triangle trigonometric ratios. [Requires Adobe Reader.]
Texas Instruments
Texas Instruments: Angle Theorem
Students use the Cabri Geometry II Plus software to investigate the relationship between angle and ratio in a right triangle.
Texas Instruments
Texas Instruments: Right Triangle Trig
This is a way to use the TI-Navigator to check for an understanding of sin, cos, and tan before you move onto word problems.
Analyze Math
Analyze Math: Special Triangles Used in Trigonometry
The trigonometry tutorial investigates special triangles. The activity includes isosceles right triangles and 30-60-90 triangles. The examples show how to obtain the six trigonometric ratios of the special angles using special triangles.