圆心角是指在中心为O的圆中，过弧AB两端的半径构成的∠AOB， 称为弧AB所对的圆心角。圆心角等于同一弧所对的圆周角的二倍。
一弧度就是长度刚好等于半径的一段圆弧所对的圆心角。
A radian is the Angle subtended by an arc of a circle whose length is just equal to the radius.
他先切下一块圆心角60度的扇形，把这块颠倒过来，糖衣放在下面。
He cuts a piece forming a circular sector of 60 degrees and flips the piece upside down, with the icing on the bottom.
根据圆弧的时间分割法插补原理，开发了基于圆心角分割的双曲线、抛物线插补算法。
According to the interpolation principle of time division of an arc, a hyperbolic interpolation algorithm and a parabolic interpolation algorithm based on central Angle division are developed.
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