Reference Table for Areas
 Topic Index | Algebra Index | Regents Exam Prep Center


"(The universe) is written in the language of mathematics, and its characters are triangles, circles, and other geometric figures, without which it is impossible to understand a single word of it; without these, one is wandering about in a dark labyrinth."

Galileo (1564-1642)

Remember to label areas with "square" units.

 Area (triangle)

 Area (equilateral triangle)

or

 Area (rectangle)

or

 Area (rectangle) = (length)•(width)

 

 Area (square)

 Area (parallelogram) 

 Area (trapezoid) 

d1=diagonal 1
d2= diagonal 2

 Area (rhombus)

or

 

 Area (circle)

Area  of sectors of circle
(Sectors are similar to "pizza pie slices" of a circle.)


Semi-circle
(half of circle = half of area)

 


Quarter-Circle
(1/4 of circle = 1/4 of area)
Any Sector
(fractional part of the area)
(optional topic)


where n is the number of degrees in the central angle of the sector.


where CS is the arc length of the sector.

                      

This area formula is an optional topic.  Perimeter of regular polygons, however, is a required topic.

Area (regular polygon)

 

Regular polygons have all sides of equal length.

a = apothem
p = perimeter