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.
Georgia State University
Georgia State University: Hyper Physics: Law of Cosines
This page from the Georgia State University provides a definition of the Law of Cosines. Also includes a "calculator" to help you find side lengths and opposite angles when you are given either three sides or two sides and a third angle.
National Council of Teachers of Mathematics
The Math Forum: Ask Dr. Math: Congruence and Triangles
This site gives a very thorough explanation of how to tell if two triangles are congruent. Dr. Math explains why SSS, SAS, ASA determine that two triangles are congruent. The Dr. gives a few exercises for the reader to try then gives the...
Integrated Publishing
Integrated Publishing: The Ambiguous Case
This page from Integrated Publishing discusses the ambiguous case, which arises in trigonometry when you are given two sides of a triangle and the angle opopsite one of them. In an ambiguous case two different triangles could conform to...
Math2
Math2.org: Trigonometry Functions
A complete look at trig functions. From an "overview," page giving general definitions and important vocab words, to a listing of the 12 trig functions, to an explanation of the three modes used in trigonometry, to the procedures of how...
Mathigon
Mathigon: Geometry: Triangles and Trigonometry: Pythagoras' Theorem
Pythagoras' Theorem: In any right-angled triangle, the square of the length of the hypotenuse (the side that lies opposite the right angle) is equal to the sum of the squares of the other two sides. (A+B=C)
Analyze Math
Analyze Math: Cosine Law Problems
Here are four problems to solve using the Law of Cosines. Two are SSS problems; two are SAS problems. Two have detailed solutions; two have answers given only. Notice the link at the bottom that takes you to a Law of Cosines calculator -...
Purple Math
Purplemath: Inverses of Trigonometric Ratios
You know that you can take side lengths and find trig ratios, and you know you can find trig ratios (in your calculator) for angles. What is missing is a way to go from the ratios back to the original angles. And that is what "inverse...
TeachEngineering
Teach Engineering: Trigonometry via Mobile Device
Students investigate the relationships between angles and side lengths in right triangles with the help of materials found in the classroom and a mobile device.
CK-12 Foundation
Ck 12: Congruence Statements
[Free Registration/Login Required] Students explore the concept of congruence statements by navigating through the interactive learning module and then answering questions that go along with the module. Students can also learn more about...
Curated OER
Science Kids: Science Images: Equilateral Triangle
This picture shows an equilateral triangle, a three sided regular polygon with internal angles of 60 degrees and sides of equal length.
Interactive Mathematics
Interactive Mathematics: Sine, Cosine, Tan & Reciprocals
The definitions of the six trig ratios are presented here, along with several examples of how to determine the ratios given 2 or more sides of a right triangle.
Ministry of Education and Universities of the Region of Murcia (Spain)
Ministerio De Educacion Y Ciencia: Razones Trigonometricas
In Spanish. In this interactive activity you will learn about the six trigonometric ratios, discover relationships between the trigonometric ratios of complementary and supplementary angles and the relationship between the sides of a...