Basic 2D shapes

2-dimensional (2D) shapes have only two dimensions, length and width.

Here are some basic regular 2D Shapes :

Rectangle

A rectangle has 4 sides (quadrilateral) and 4 right angles, its opposite sides are equal, and they are parallel to each other and it has 2 lines of symmetry and rotational symmetry order 2.

To calculate the area of a rectangle, multiply its length by its width (The answer will be a square measure, for example: cm2)

To calculate the perimeter of a rectangle, add up the length of all sides.

Square

Square has 4 equal sides (quadrilateral) and 4 right angles, it has 2 pairs of parallel sides, it has 4 lines of symmetry and 4 rotational symmetry.

To calculate the area of a square, multiply its length by its width (The answer will be a square measure, for example: cm2)

To calculate the perimeter of a rectangle, add up the length of all sides or you can multiply the length of one side by 4 as the length of all sides equal.

Circle

A circle has no sides and no angles -as you see.
All points on the edge of the circle are at the same distance from the centre.

A circle has infinite number of line of symmetry and infinite order of rotational symmetry.

The distance from the centre to the all point on the edge called radius (plural : radii) and the whole line from edge to another called diameter.
To find out the diameter of a circle just double the radius (radius * 2)

The perimeter of a circle called “circumference” which is the whole line around the circle.

To find out the circumference of a circle we use this formula : C = π d
π = 22/7 ≈ 3.14
d = The diameter of the circle

Parallelogram

A parallelogram has 4 sides (quadrilateral) 4 angles, its opposite sides are equal and they are parallel to each other, the opposite angles of a parallelogram are of equal measure, it has 2 lines of symmetry and rotational symmetry order 2.

The difference between a parallelogram and a rectangle is that a rectangle has 4 right angles but a parallelogram has opposite equal angles but not right angles.

Triangle.Equilateral.svg
Equilateral Triangle

There are more than one type from triangles this one in the picture is an Equilateral Triangle, it has 3 equal-sides and 3 equal-angles, the bottom side called “the base”

To find out the area of a triangle you multiply the perpendicular height, which is the line from the meddle of the base to the top angle, by length of the base and then divide by 2 .