# The Sine Rule (Law of Sines)

Investigating the Sine Rule (Law of Sines) for non-right-angled triangles.

UK Years 10-12, KS4, KS5, Higher GCSE Mathematics, Grades A - A* - Shape, Space and Measure

US - Grades 10-12 - Geometry

Instructions below See also: The Cosine Rule and Area Formulas PRINT

The formulas for the Sine Rule are: or

## How to Use this Applet

On the screen you'll see a triangle, which you can move and change by clicking and dragging the vertices (corner points A, B and C) with the mouse.

You can choose what kind of calculation you would like to see from the drop-down menu at the top of the screen.

The calculations of sides and angles are seen on the right.

If you are using the Sine Rule to find an angle then be careful! There are two possible answers each time. You must decide whether the angle is acute or obtuse. Learn by observing.