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Formula for circumference of a semicircle: πr
Formula for perimeter of a semicircle: πr+2r
Formula for area of a semicircle: ½×πr2
Arc: A part of the circumference of a circle.
Two points on a circumference of a circle will create two arcs:
The smaller arc is known as the minor arc
The bigger arc is known as the major arc
Sector: A sector is the part of a circle enclosed by two radii (radiuses) and an
arc.
Two radii in a circle will create two sectors:
The smaller sector is known as the minor sector
The bigger sector is known as the major sector
A circle with a marked sector in blue
In the above diagram, the minor sector is the red area and the blue area,
whereas the segment is just the blue area. The minor arc is the arc connected
to the blue area, whereas the major arc is the rest of the circumference.
The area of any minor sector with angle theta (θ) is θπr2/360°.
The arc length of any arc with angle theta bound to its corresponding radii is
θπr/180°.
The perimeter of any sector with angle theta is θπr/180° + 2r.
Volume and Surface Area
Volume: The space taken up by a 3-D object. The three dimensions are
length, width/breadth, and height/depth.