# Law of Cosines Calculator

Law of Cosines Calculator is a free online tool that displays the measure of unknown side or angle using the law of cosines. BYJU’S online law of cosines calculator tool makes the calculation faster and it displays the unknown angle or side in a fraction of seconds.

## How to Use the Law of Cosines Calculator?

The procedure to use the law of cosines calculator is as follows:
Step 1: Enter the side length and the angles in the respective input field
Step 2: Now click the button “Find Third Side Length / Find Angle” to get the result
Step 3: Finally, the unknown side or the angle using the law of cosines will be displayed in the output field

### What is Meant by the Law of Cosines?

In mathematics, the law of cosine is also known as the cosine law, which is used to find the sides or angles of a triangle. This law relates the length of the triangle to one of its cosine angles. The cosine rule is mostly preferred when three sides of the triangle are given (SSS) or the two sides and one angle (SAS) is given. The formula to find the sides of the triangle using the law of cosine is given by

• a2 = b2 + c2 – 2bc cos (A)
• b2 = a2 + c2 – 2ac cos (B)
• c2 = a2 + b2 – 2ab cos (C)