C2: The sine and cosine rule
Sine Rule

Cosine Rule

You may well have come across the Sine and Cosine rules at G.C.S.E.
When you first got taught trigonometry (SOHCAHTOA), you only considered triangles where there is a right angle. The Sine and Cosine rules allow you to work out lengths and angles in any triangle, regardless of whether there is a right angle or not.
We are going to study these one at a time.
The Sine rule is for triangles where there are two lengths and two angles  and you are asked to work out one of these.
The Cosine rule is for triangles where there are three lengths and one angle  and you are asked to work out one of these.
This work also gets used in M1 where you have to work out problems involving ships or planes.
It is also sometimes used in C4 when you study vectors and you have to work out the distance of a line from the origin.
When you first got taught trigonometry (SOHCAHTOA), you only considered triangles where there is a right angle. The Sine and Cosine rules allow you to work out lengths and angles in any triangle, regardless of whether there is a right angle or not.
We are going to study these one at a time.
The Sine rule is for triangles where there are two lengths and two angles  and you are asked to work out one of these.
The Cosine rule is for triangles where there are three lengths and one angle  and you are asked to work out one of these.
This work also gets used in M1 where you have to work out problems involving ships or planes.
It is also sometimes used in C4 when you study vectors and you have to work out the distance of a line from the origin.
