2/4/25, 3:01 PM Radian
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Radian
1.1 Radian
Mind map titled 'Radian' illustrating the formula for converting radians to degrees.
Definition of One Radian
Definition
The angle subtended at the centre of a circle is 1 radian if the length of the arc is equal to the radius of the circle.
Figure
Relationship with Degrees
180∘
1 rad =
π
360∘ = 2π rad
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2/4/25, 3:01 PM Radian
Conversion Formula
To convert degrees to radians:
π
radians = degrees ×
180∘
To convert radians to degrees:
180∘
degrees = radians ×
Example 1
Question
Convert 120∘ to radians.
Solution
π
radians = 120∘ ×
180∘
2π
= rad.
3
Example 2
Question
π
Convert rad to degrees.
4
Solution
∘
π 180
degrees = rad ×
4 π
= 45∘ .
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