Home >> PURE MATHS, Trigonometry, sine & cosine rules

The Sine Rule

Use any pair of equalities.

In the triangle you are given 3 quantities and required to work out the 4 th.

Manipulating the Ratio

Take two ratios, cross multiply and rearrange to put the required quantity as the subject of the equation.

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Example #1

Example #2

Example #3

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The Cosine Rule

There are two problem types:

You are given 2 sides + an included angle and required to work out the remaining side.

You are given all the sides and required to work out the angle.

Example #1

Example #2

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