Steply

Angle at the edge 48, angle at the center x

Step by step, with the reason for every step · Circle rules · Geometry

Step by step

The question

Question: find x.

The angle at the center is x.

The angle at the edge is 48°.

1 Use the circle rule

O is the center of the circle.

Lines from A and B to the center make the angle at the center.

Lines from A and B to C, on the edge, make the angle at the edge.

Both angles stand on the same arc: the orange part of the circle, from A to B.

Circle rule: the angle at the center is double the angle at the edge.

This is always true.

So x is double 48: x = 2 × 48.

x = 2 × 48

2 times 48 is 96.

So x = 96.

x = 96

2 Check

Let's check: double 48°.

2 × 48 = 96

96° is double 48°.

So x = 96 is right!

Let's look back.

First: use the circle rule.

Last: check.

Answer
x = 96

Your turn

Try this one yourself, then check:

Find x.
Show the answer
x = 90°

More from Circle rules

The whole lesson: Circle rules →