Idea 9of 24Builds onTwo scales: start at the 0
Draw an angle with a protractor
How do you draw an angle of exactly 70°?
Today you'll discover
- what to draw before using the protractor
- where to put the dot
- how to finish the angle
Think firstDraw a 70° angle on this arm
You have one arm and its vertex. What do you do next?
Decide first, then press Next. Watch where the dot goes, then the new arm.
One arm pointing right from a dot, its vertex. A protractor slides onto it, centre on the vertex and 0 along the arm. A dot is marked at 70 on the inner ring, then a new arm is drawn from the vertex through the dot, making a 70° angle. The last step shows an arm pointing left, with 120° still to be drawn.
See the whole ideathe big idea and the key word, in one place
The big idea
Line up the protractor on one arm, mark the size, and join that mark to the vertex.
Four stepsDraw one arm with a ruler. Line up the protractor: centre on the vertex, 0 on the arm. Mark a dot at the size. Join the dot to the vertex.
Easy to get wrongCount on the ring whose 0 is on your arm. The other ring gives the angle that is left over from 180°.
Key word
- construct
- draw exactly to given measurements, using tools like a ruler, a protractor or a compass
Ready to use it?
- Construct an angle of a given size with a protractor.