A POLYGON WITH THREE SIDES.

RECTANGLEA box shape on a plane. Formally, a

rectangle is a quadrilateral with

four congruent angles (all 90°).

The perimeter of a parallelogram:

To find the perimeter of a parallelogram, just add up all the lengths of the sides:

Perimeter = a + b + a + b = 2a + 2b

The area of a parallelogram:

To find the area of a parallelogram, just multiply the base length (b) times the height (h):

Area = b x h

PARALLELOGRAM

CircleThe locus of all points that are a fixed distance from a given point.

AB = DiameterMust pass through the center of the circle. The Diameter is equal to twice the radius.

OC = RadiusThe radius is a line segment that begin from the center and touches any point on the circle.

ED = ChordThe chord joins any two points on a circle.

FG = TangentA line with one point common to the circle.

EHD = ArcOnly the portion of the circle that is between two points on the circle.

ADB = SemicircleAlso considered to be an arc that is exactly half of the circle.

OCB = SectorThe area between two radii and the arc.

COB = Central AngleFormed by two radii

CIRCLES

A regular octagon is a closed figure with sides of the same length and internal angles of the same size. It has eight lines of

reflective symmetry and rotational symmetry of order 8. The internal angle at each vertex of a regular octagon is 135° and

the sum of all the internal angles is 1080° (as for any octagon). The area of a regular octagon of side length a is given by

In terms of R (circumradius), the area is

In terms of r (in radius), the area is

IRREGULAR SHAPES