Page 13 - Grab Me SPM Add Mathematics Form 4,5

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Geometry
CHAPTER 1 CIRCULAR MEASURE

1.1 Radian • Conversion of degrees to radians and vice versa:
× π
• One radian is a measure of the angle subtended 180°
at the centre of a circle by an arc of equal length Degrees Radians
to the radius of the circle. × 180°
π
B Example:
r r (a) 100° = 100° × π = 1.745 rad
180°
1 rad 180°
O r A p rad = 180° (b) 0.7 rad = 0.7 × π = 40.11°
Example 1
y
The diagram on the right
180° shows a circle with centre
Hence, 1 rad = ≈ 57.29° β
π O which is divided into eight α
π equal parts. x
and 1° = ≈ 0.01746 rad O
180° θ
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Ch 1_Grab Me SPM AddMaths F5.indd 119 13/05/2022 9:06 AM