# Triangles

In this lesson we shall cover

• Introduction to Core 2
• Labelling a non-right angles triangle
• Sine Rule for length
• Sine Rule for Angles
• The ambiguous Sine rule case
• Cosine Rule for length
• Cosine Rule for angles
• Summary of the Sine and Cosine Rules
• Area of a Triangle
• Finding the midpoint
• Finding the distance
• Putting Everything Together

## Introduction to Core 2

A few things we need to know before we start Core 2 mainly that you can use a calculator and will need one for this session.

## Labelling a non-right angles triangle

Here we will learn how you will need to label non right angles triangles which will be required for the rest of this lesson.

## Sine Rule for length

We look at the formula for the sine rule for length which was given to you in your GCSE exam, this time you need to memorise it. We will go through a variety of examples on this.

## Sine Rule for Angles

You need to convert the formula for the sine rule for lengths to get the rule for angles, once again, this formula will not be provided in your exam. We will cover some examples of these.

## The ambiguous Sine rule case

This is an unusual case where a triangle is described to you and you are asked to calculate the missing angle. The thing is there are two ways to draw that triangle, but most students can only think of the first way. We will also show you a short cut method.

## Cosine Rule for length

This formula was provided at GCSE and is still provided at A-Level, however we recommend you memorise this formula to speed up your work. We will cover a few examples of this together.

## Cosine Rule for angles

To find the formula for this section you will need to rearrange the formula for the cosine rules for length and make cos A the subject of it which we will cover in this section. Don’t forget the get the answer at the end you will be required to do an inverse cos to get the angle. We will do a few examples of these.

## Summary of the Sine and Cosine Rules

Now that you know the formulae, you need to know when to use what formula. The table we have created will make things very simple to follow.

## Area of a Triangle

We will learn the formula for the Area of a Triangle which you should have covered at GCSE and we will do a few examples of these.

## Finding the midpoint

The formula for finding the midpoint between two co-ordinates, although we have covered this in Core 1, we will do a quick recap with a few examples.

## Finding the distance

Another section we will have covered in the Core 1 module but will be doing a quick recap of finding the distance between two points with a few examples

## Putting Everything Together

This section will be a summary of the whole lesson and we will use most of the sections above and more to answer the questions in this section.

## Lesson Resources

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