More Lessons for Grade 9 Math

Math Worksheets

Videos, worksheets, solutions, and activities to help students learn how to use the law of cosines.

The Law of Cosines

One method for solving for a missing length or angle of a triangle is by using the law of cosines. The law of cosines is similar to the Pythagorean theorem, but it works for all triangles, not just right triangles. In order to understand how to use the law of cosines effectively, one must understand the cosine function and inverse trigonometric functions.

Learn how to solve a triangle using the law of cosines.

Introduction to the law of cosines to solve for a side of a triangle when 2 sides and an angle are known

In this video, I give the formula for the 'Law of Cosines' and do one 'applied' example.

Rotate to landscape screen format on a mobile phone or small tablet to use the **Mathway** widget, a free math problem solver that **answers your questions with step-by-step explanations**.

You can use the free Mathway widget below to practice Algebra or other math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.