2D SHAPES

CIRCLE

A circle is a closed 2d figure in which the set of all the points in the plane is equidistant from a given point called the “Center”.

The distance from the Center to the outer line of the circle is called a radius.

Area of a Circle = πr²

Radius (r) = (Diameter)/2

Diameter (d) = 2 × radius

Circumference of a circle = 2πr

Related pages

• Find the area of a circle
• Problems on finding area of circle worksheet
• Problems on finding area of circle
• Find the radius and diameter of each circle
  
• Find the circumference of the circle

TRIANGLE

A triangle is a three-sided polygon (2d Shape) that has three edges and three vertices.

The sum of all the three angles of a triangle is equal to 180°.

Area of a triangle = 1/2 × base × height

Perimeter = a + b + c

(where a, b, and c are the sides of a triangle)

Related pages

Area and Perimeter of Triangle

• How to Find the Area of a Triangle
• Find the Perimeter of Each Triangle
• Finding the area of triangle with base and height
• Find Missing Side When Given Perimeter
• Finding the area of a regular polygon using special right triangles

Angles and Sides of Triangle

• Classifying Triangles Based on Side Measures
  
• Classifying Triangles Based on Angles Measures
  
• Finding Angle Measures of a Triangle Using Ratios
  
• Finding Missing Angles in Triangles
  
• Find the Length of a Missing Side of a Right Triangle
  
• Problems on angles of triangle
• Determine whether the triangles are similar
  
• Special right triangles

SQUARE

A square is a four-sided polygon (2d Shape), whose four sides are equal in length and all the angles are equal to 90°. 

It is considered to be a two-dimensional regular quadrilateral. 

The diagonals of the square also bisect each other at 90°.

Area of a Square = a²

(where a is the side of a square)

Area of a square using diagonals = 1/2 × d²

Perimeter of a square = 4 side

Perimeter of a square using diagonals = 2√2 × d

Related pages

• Area and perimeter of square
• Find area of square when diagonal is given
• Find the length of the diagonal
• Problems involving diagonal of a square worksheet 
• How to find diagonal of square

RECTANGLE

A rectangle is a 2d shape that has four sides, where the opposite sides are equal and parallel to each other.

All the angles of a rectangle are equal to 90°.

Area of a Rectangle = Length × width

Perimeter = 2(Length + Width)

Related pages

• Area and perimeter of rectangle
  
• Problems on diagonal of a rectangle
• Problems on diagonals of a rectangle worksheet
• Properties of rectangle
• Properties of rectangle worksheet
• Practice problems on properties of rectangle
  
• Word problems on area of rectangle worksheet
• Problems on diagonal of a rectangle worksheet

PARALLELOGRAM

A parallelogram is a two-dimensional geometrical shape, whose sides are parallel to each other. 

It is a type of polygon having four sides (also called quadrilateral), where the pair of parallel sides are equal in length.

The Sum of adjacent angles of a parallelogram is equal to 180 degrees.

Area of a parallelogram = Base x height

Height = Area / Base

Base = Area / Height

Perimeter of a parallelogram = 2(a + b)

(where a and b are the sides)

Related pages

• Finding the area of parallelogram
• Find the perimeter of each parallelogram
  
• Find the base and height of a parallelogram
  
• Solve unknown values in each parallelogram
  
• Find the indicated angle in the parallelogram with diagonals
• Find missing angles in parallelogram
• Find missing angles of parallelogram worksheet
• Length of diagonal of parallelogram
• Length of diagonal of parallelogram worksheet
• Properties of parallelogram worksheet

RHOMBUS

A rhombus is a 2D shape with four straight, equal sides with both pairs of opposite sides being parallel.

The total distance travelled along the border of a rhombus is the perimeter of a rhombus.

Area of a rhombus = 1/2 × d₁ × d₂

(Where d₁ and d₂ are the diagonals of the rhombus)

Perimeter of a rhombus = 4a 

(where a is the length of the side of the rhombus)

Related pages

• Finding the missing diagonal of a rhombus
• Problems on diagonals of rhombus
• Applying properties to find side length of rhombus
• How to find missing angles of rhombus with diagonals

Trapezium

What is trapezium ?

A trapezium is a quadrilateral which has a pair of parallel opposite sides.

Related Pages

• Finding the area of a trapezoid
• Find the missing dimension of a trapezoid
  
• Area of trapezoid worksheet
  

Kite

Definition of kite :

A kite is a quadrilateral which has two pairs of adjacent sides equal in length.

Related Pages

• Finding the missing diagonal of a kite
• Finding diagonal measure of a kite worksheet
  
• Geometry problems on properties of kite
• Geometry problems on properties of kite worksheet

Polygon

What is polygon ?

A polygon can be defined as a flat or plane, two-dimensional closed shape with straight sides. It does not have curved sides.

Regular polygon :

A polygon having equal sides and equal angles is a regular polygon.

To find area of regular polygon, we use the formula 

What is Apothem ?

A line from the center of a regular polygon at right angles to any of its sides.

Related Pages

• Finding area and perimeter of regular polygon
• How to find area of regular polygon
• Find area of regular polygon using special right triangles
• Polygons on the coordinate plane
• Problems on interior angles of polygon
• Find measure of interior angles of regular polygon
• Problems on regular polygon
• How to find number of sides of polygon with one one interior angle
• Interior angles of a regular polygon worksheet
• Finding number of sides of a polygon worksheet
  
• Interior and exterior angles of polygons worksheet
  
• Problems on interior and exterior angles of a polygon
  
• Find the number of sides of the polygon if exterior angle given
  
• Find the missing interior and exterior angles of a polygon