Here are two arms joined at one corner. I can open them a little to make a small turn. I can open them a lot to make a big turn. Watch what happens to the angle when I make one arm longer but do not open the arms any wider.

Today we make turns with the joined arms and test them against a square corner. Make:

• the smallest opening you can
• a square-corner turn
• a turn wider than a square corner
• two openings side by side — which is the bigger turn?

Now you make and compare turns yourselves. At your seats with your own joined arms, make:

• the smallest opening you can
• a square-corner turn
• a turn bigger than a square corner
• two openings — which is the bigger turn, and how do you know?