# Unit 5 Section 5 : Constructing Triangles

In this section you will see how to construct triangles.
You will need some paper, a pencil, a protractor and a pair of compasses.

WARNING : Do not attempt to construct triangles on the computer screen - you will damage it!

## Example 1

Below is a triangle which we want to draw accurately.
Click where it says Click here to begin to see how to do this construction.
When you have done each stage on paper, click on the right-hand image again to see the next step.
You have finished when you see a big tick, but you can continue clicking to see the process again.

## Example 2

Below is another triangle which we want to draw accurately.
Click where it says Click here to begin to see how to do this construction.
When you have done each stage on paper, click on the right-hand image again to see the next step.
You have finished when you see a big tick, but you can continue clicking to see the process again.

## Exercises

Work out the answers to the questions below and fill in the boxes. Click on the button to find out whether you have answered correctly. If you are right then will appear and you should move on to the next question. If appears then your answer is wrong. Click on to clear your original answer and have another go. If you can't work out the right answer then click on to see the answer.

In these questions you need to do some constructions and then answer questions about them.
Do the constructions on paper and then fill in the answers on the web page.

Question 1
Construct each of these triangles accurately on paper. Measure the angles in each triangle and write them on your page.

 What did the three angles in each triangle add up to? (you should have the same answer for all four triangles) º

Question 2
Some triangles can not be constructed. Think about a triangle with sides of length 12cm, 5cm and 4cm.
If you draw the base of 12cm, the other two sides aren't long enough to join up with each other. Try it!

 Which of these triangles is it possible to draw? (a) Possible Not possible (b) Possible Not possible (c) Possible Not possible (d) Possible Not possible

Question 3
Accurately construct the triangle below on paper, then measure the other lengths and angles.

 What is the length of the line between A and B? cm What is the length of the line between B and C? cm What is the angle at B? º What do the three angles in the triangle add up to? º

Question 4
Try and work out the size of the third angle in each of the triangles below.
You should also construct the triangles on paper to check the answers.
 Type in the sizes of each missing angle below: (a) º (b) º (c) º (d) º

You have now completed Unit 5 Section 5
 Your overall score for this section is Correct Answers You answered questions correctly out of the questions in this section. Incorrect Answers There were questions where you used the Tell Me button. There were questions with wrong answers. There were questions you didn't attempt.
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Produced by A.J. Reynolds January 2001