Angles at a point

Lesson

An angle is made when $2$2 rays (lines) meet at a common point or vertex.

We measure the size of angles with reference to a circle with a centre at the common vertex.  An angle that turns through $\frac{1}{360}$1360 of a circle is called a "one-degree angle".

That means that if we have a number of one-degree angles, we can add then together to find the total size of that angle. For example, an angle that turns through $12$12 one-degree angles would have an angle measure of $12^\circ$12°. The angles in a circle add up to $360$360 degrees.

If we know that the angles in a circle add up to $360$360 degrees we can work out the values of unknown angles in a circle.  Look at this demonstration to see how.

Remember!

The angles in a circle add up to $360^\circ$360°.

Worked Examples

QUESTION 1

Find the size of the unknown angle $x$x.

QUESTION 2

Find the size of the unknown angle $x$x.

QUESTION 3

$12$12 equal angles add up to one whole revolution. What is the measure of each angle?