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IntroductionRadians, like degrees, are a way of measuring angles.
Due to their usefulness, people often omit the symbol for radians. It is written in a similar way to degrees, ie one radian would be written Now, the circumference of the circle is Therefore to convert a certain number of degrees in to radians, multiply the number of degrees by p/180 (for example, 90º = 90 × p/180 radians = p/2). To convert a certain number of radians into degrees, multiply the number of radians by 180/p . Arc LengthThe length of an arc of a circle is equal to rø, where ø is the angle, in radians, subtended by the arc at the centre of the circle. So in the below diagram, s = rø .
Area of SectorThe area of a sector of a circle is ½ r² ø, where r is the radius and ø the angle in radians subtended by the arc at the centre of the circle. So in the below diagram, the shaded area is equal to ½ r² ø .
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