Shape/Description

Visual
representation

Perimeter (p)

Area (A)








Polygon
A closed plane figure that has three or more straight sides and angles
OR
A polygon with n sides and n angles has the sum of the angles = (n2)*180˚
Examples of polygons are: Triangle (3 sides); Quadrilateral (4 sides); Pentagon (5 sides); Hexagon (6 sides); Heptagon (7 sides); Octagon (8 sides); Nonagon (9 sides); Decagon (10 sides) and so on.

Triangle
A polygon with 3 sides and 3 angles
The sum of the triangle’s angles is equal with 180˚

Scalene
triangle
A triangle with unequal sides and therefore unequal angles.

Obtuse
scalene
triangle
A triangle with one of the angles larger than 90˚.
In this case the angle A is larger than 90˚.




Acute
scalene
triangle
A triangle that has no angle larger than 90˚.


Isosceles triangle
A triangle that has two sides and therefore two angles equal.
In this case AB = AC and angle B is equal with angle C.


Equilateral triangle
A triangle that has all sites and angles equal.
In this case AB = BC =CA and angle A = angle B = angle C.


Right triangle
A triangle that has one of its angle 90˚ therefore the two adjacent sites are perpendicular on each other.
In this case angle A = 90˚ and therefore AC is perpendicular on AB and reverse (AB is perpendicular on AC).


Quadrilateral
A polygon with 4 sides and 4 angles.
The sum of the quadrilateral’s angles is equal with 360˚

Quadrilateral
(general shape)




Parallelogram
A quadrilateral that has the opposite sides equal and the opposite angles equal.
In this case AB = CD; AC = BD; angle A = angle D and angle B = angle C.



Rhombus
A parallelogram that has all sides equal.



Rectangle
A parallelogram that has all angles equal with 90°.



Square
A rectangle that has all sides equal.



Trapezoid
A quadrilateral with two opposite parallel sides, bases and two lateral sides, legs, that are not parallel.

Scalene trapezoid
A trapezoid that has no equal sides or angles.



Right trapezoid
A trapezoid that has two adjacent angle equal with 90°.
In this case angle A = angle C = 90°.


Isosceles trapezoid
A trapezoid that has equal legs and equal adjacent angle.
In this case AC = BD and angle A= angle B and angle C = angle D.


Polygon (general shape)
A polygon with n sides and n angles
has the sum of the angles = (n2)*180˚
in our example therefore the sum of the angles
OR:
There are 5 triangles inside this heptagon (a polygon with 7 sides). One triangle has the sum of its angle therefore the polygon will have 5 times the sum of the trianle’s angles (


in our example:

(triangles that form the polygon)
In our example:

Circle
A closed plane curve which points are equidistant from a fixed point, the center.
OR
A set of points equal distanced from a point, the center.

Circle



(when area is function of R)
or
(when area is function of D)

Circle sector
A circle sector is the portion of a circle in between two radii.


where:
if is in degrees
and,
if is in radians

if is in degrees
and,
if is in radians

Circle segment
A circle segment is the portion of a circle in between a chord and the arc that has same end points as the chord.


where has same formula as for Circle sector and
Look here for formula.

if is in degrees
and,
if is in radians

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