Lesson

We've seen how angles are all around us, and looked at how to compare one angle to another. Now we are going to look at two special angles.

One of the most important angles is the right angle, or $90$90 degree angle.Do these clocks give you a clue what a right angle might look like?

In Video 1, we look at right angles, and then check some angles to see if they are right angles or not.

Although it doesn't look as if we have an angle, a horizontal line is in fact an angle of 180^{o}. We call that a straight angle. Here are our clocks again. Can you spot the straight angles?

Let's look at some angles to see if they are right angles or straight angles, in Video 2.

Remember!

A right angle is the same as rotating one quarter of a turn. A straight angle is like rotating half a turn, or two quarters of a turn.

Classify plane shapes and prisms by their spatial features