Let be the radius of the circle. What is the angle subtended by an arc of length at the center of the circle?
(A) 1 degree
(B) 1 radian
(C) 90 degrees
(D) π radians
Explanation: Radian describes the plane angle subtended by a circular arc as the length of the arc divided by the radius of the arc. One radian is the angle subtended at the center of a circle by an arc that is equal in length to the radius of the circle.
Note that 1 radian = 57.2958 degree.
So, option (B) is correct.
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