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India
Class VII

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?

Outcomes

7.G.US.1

Pairs of angles (linear, supplementary, complementary, adjacent, vertically opposite) (verification and simple proof of vertically opposite angles)

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