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 righthand 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 righthand 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)


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!
Question 3
Accurately construct the triangle below on paper, then measure the other lengths and angles.
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.
You have now completed Unit 5 Section 5
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Produced by A.J.Reynolds January 2001