Let this be the angle d theta so it moves in a short amount of time over an angle d theta dS and the arc here is dS, R and the radius is R.
这是角度dθ,它运动了一会儿,运动过角度dθ,弧度是，半径是。
2
The tiny but intriguing yellowish arc visible near the blue nebulae marks young variable star R Coronae Australis.
在蓝色星云附近，微小但迷人的微黄色弧状可见物标出了年轻可见恒星南冕座R星的位置。
3
In this paper, a method-ARC method is introduced, by which the development chart can be drawn, of multiple-piece, equal-diameter and right-angled elbows with the radius as the arc of r.