cosine

詳細解釋：

co.sine

n.Abbr. cos（名詞）縮寫 cos
In a right triangle, the ratio of the length of the side adjacent to an acute angle to the length of the hypotenuse.
餘弦：直角三角形銳角邊的邊長與敘邊的比
The abscissa at the endpoint of an arc of a unit circle centered at the origin of a Cartesian coordinate system, the arc being of lengthx and measured counterclockwise from the point (, 0) if x is positive or clockwise if x is negative.
餘弦：以笛卡兒坐標系原點為圓心的單位圓的圓弦端點的橫坐標，弧的長度為x ，如果 x 為正，弧的長度則從（，0）點按逆時針方向算起，若 x 為負，則按順時針方向從（，0）點算起