Loading please wait

The smart way to improve grades

Comprehensive & curriculum aligned

Try an activity or get started for free

Label Sides of a Triangle

In this worksheet, students will become familiar with labelling sides of a triangle to help solve trigonometry problems.

'Label Sides of a Triangle ' worksheet

Key stage:  KS 4

GCSE Subjects:   Maths

GCSE Boards:   AQA, Eduqas, Pearson Edexcel, OCR,

Curriculum topic:   Geometry and Measures, Mensuration

Curriculum subtopic:   Mensuration and Calculation Triangle Mensuration

Difficulty level:  

Worksheet Overview


man on a mountain                  sailing           


How can you find the height of this mountain?

How can this mountaineer draw an accurate map?

How did sailors navigate before GPS?

How can computers rotate images so that they can be viewed from many different directions?



They look at angles and sides of triangles and make connections between them.

This is pretty cool stuff really.


This is called Trigonometry.


Trigonometry is concerned with calculating the sides of triangles, angles within them.

There are three important ratios that you will need to know.  Sine, Cosine and Tangent. 

These ratios are in terms of the sides of a right angled triangle and an angle.

Before you can solve anything using Sine, Cosine and Tangent accurately, you need to be able to label the triangles correctly.


Things to remember

The longest side of a right angled triangle is called the hypotenuse (H)

The side opposite the angle is called the opposite side (O)

The side right next to the angle is called the adjacent side (A)


trig ratio

Look at the diagram above.

Label the hypotenuse first, as it is the easiest to spot.

Then go to the angle and pick up the opposite side.

That just leaves the adjacent side to label.

I always do it in that order, as it can be easy to get the opposite and adjacent muddled up.


Now let's look at labelling the adjacent.

trig ratios

When you want to find the adjacent angle, find the angle in your diagram and draw a line along the side

Let's tri...  

What is EdPlace?

We're your National Curriculum aligned online education content provider helping each child succeed in English, maths and science from year 1 to GCSE. With an EdPlace account you’ll be able to track and measure progress, helping each child achieve their best. We build confidence and attainment by personalising each child’s learning at a level that suits them.

Get started

Try an activity or get started for free

  • educational
  • bettfutures
  • cxa
  • pta
  • era2016
  • BDA award
  • Explore LearningTuition Partner
  • tacm