# Sine Rule

The *sine and cosine rule* works for non-right angled triangles and, and therefore finds the length of sides and size of angles for
*any* triangle. This article consists of a calculator, example questions,
and proof. The sine rule is a *general-purpose* formula that works for many types of triangles including scalene where all the sides are of a different length and all the angles are different. If you are studying to become a pilot then you will need to know how to solve vectors and this rule can be very handy sometimes. It might be useful for GCSE, and kids, or just about anyone who wants to learn how to solve angles.

## Formula

The formula is very simple to remember because; the ratio, which consists of the length of a side divided by the sine of the opposing angle, is same for all three sides and angles.

## To Find an Angle

To *find an angle*, you must have one angle and two sides of the triangle under investigation. For angle B, you need side b, side a, and angle A. You then have to do an inverse sin, commonly known as arcsine to find the angle.

## To Find a Side

To find a side, you must have two angles and one side of the triangle to be able to find a side. For example if you want to find the side a, then you will need side b, angle A, and angle B.

## This Article Continues...

Sine RuleSine Rule Calculator

Sine Rule Questions

Sine Rule Proof