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# Sine and Cosine Rules in 3D

### Sine and Cosine Rules in 3D

We can use the Sine and Cosine rules to work out angles and sides in 3D shapes.

We can construct triangles from the vertices of 3D shapes and use trigonometry to find unknown angles and sides.

This is the Sine rule

We can use this to find unknown angles or sides given 2 angles and a side, or 2 sides and an angle.

This is the Cosine rule

We can also use this to find unknown angles and sides given an angle and two sides

This is Pythagoras' Theorem

We can use Pythagoras' to find out an unknown side as long as we know the length of the other two sides.

Let's have a go at applying some of these rules to problems involving 3D shapes.

We can also make use of the **sine rule** and **cosine rule** in order to find unknown angles or sides in 3D shapes.