Step by step
The question
Question: change 240° to radians.
1 Write the rule
Radians are another way to measure an angle.
A half turn is 180°.
In radians, a half turn is π.
So 180° = π.
180° = π
We divide both sides by 180.
One degree is π/180.
1° = π180
Careful!
To get radians, π must end up in the answer.
So π goes on top.
Careful: to radians: × π180
2 Multiply
240° is 240 times one degree.
So we multiply 240 by π/180.
240° = 240 × π180
Top times top: 240π.
The bottom stays 180.
240° = 240π180
3 Make it simpler
240 and 180 can both be divided by 60.
It is the biggest number that goes into both.
240 ÷ 60 is 4.
180 ÷ 60 is 3.
240 ÷ 60 = 4
180 ÷ 60 = 3
So 240° = 4π/3 radians.
240° = 4π3
4 Check
Let's check: go back to degrees.
Times 180° over π: the πs cancel.
4π3 × 180°π = 4 × 180°3 = 240°
We get 240° again: the angle we started with.
So it is right!
Let's look back.
First: write the rule.
Then: multiply.
Then: make it simpler.
Last: check.
Answer
240° = 4π3