The algebraic value of an arc is its length, the value of a sector is its area.
Marking two points A and B produces a semicircle above the segment AB.
Marking three points M, A and B produces a circular arc with center M, starting point A and endpoint B. Note: point B does not have to lie on the arc.
Marking three points M, A and B produces a circular sector with center M, starting point A and endpoint B. Note: point B does not have to lie on the sector.
Marking three points produces a circular arc through these points.
Marking three points produces a circular sector through these points.