Cosine Rule

Rate this resource

The first sheet of this interactive excel file shows a triangle ABC with the lengths of appropriate sides labelled a, b, and c. The six versions of the Cosine Rule are shown with each side and the cosine of each angle as the subject of the formula.

The next sheets require students to carry out calculations. One sheet shows a triangle with the lengths of two sides and the included angle given so that the remaining side can be calculated. The next sheet is about finding angles given the three sides. Answers can be revealed and new questions generated.

The final interactive sheet shows a table with pieces of information about lengths and angles of triangles so that other dimensions can be calculated.

There are a further four sheets of questions which may be suitable for use in the classroom.


This program was designed by be viewed on a screen with a resolution of 1024 x 768. Users may have to adjust the resolution of their screen for the pages to display as was originally intended. The program uses macros which need to be enabled on users' machines.

Show health and safety information

Please be aware that resources have been published on the website in the form that they were originally supplied. This means that procedures reflect general practice and standards applicable at the time resources were produced and cannot be assumed to be acceptable today. Website users are fully responsible for ensuring that any activity, including practical work, which they carry out is in accordance with current regulations related to health and safety and that an appropriate risk assessment has been carried out.

Show downloads

Published by


Share this resource