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Math Help - What is a radian?

  1. #1
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    What is a radian?

    What is a radian? A radian is the measure of an angle at the centre of a circle subtended by an arc, whose arc length is equal to the radius of the circle: Not exactly what this means.

    When I am looking for arc length I can find the circumference around the circle then take the fraction of the angle that I am given to the whole circle.

    If I use the formula S=(thata)r
    thata has to be in terms of radians-- why?
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  2. #2
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    Quote Originally Posted by algebraisabeast View Post
    What is a radian? A radian is the measure of an angle at the centre of a circle subtended by an arc, whose arc length is equal to the radius of the circle: Not exactly what this means.
    If you do not know what a centeral angle of a circle, then you must start there.

    In a circle of radius 10, any centeral angle of 1.5 radians will subtend an arc of 15 units.
    That is (1.5)(10).
    A centeral angle of 1 radian will subtend an arc of 10 units.
    A centeral angle of 3 radians will subtend an arc of 30 units.
    A centeral angle of 2\pi radians will subtend an arc of 20\pi units the whole circle.
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