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# Plane Figures

The word “Plane” in dictionary says,

• Level
• Flat surface
• For smoothing surface

In math, plane is defined as the levelled flat smooth surface.

Plane figures are those figures which are closed and has smooth levelled flat surface.

Plane figures boundary could be straight lines or curved lines or both.

Illustration:

 It is a plane figure since it is closed The boundary of the plane figure is a curved line It is a plane figure since it is closed The boundaries of the plane figure has straight and curved lines. It is a plane figure since it is closed The boundary of the plane figure has straight lines. It is a plane figure since it is closed The boundaries of the plane figure has straight and curved lines. It is a plane figure since it is closed The boundary of the plane figure has straight lines.
 It is not a plane figure since it is not closed. It is not a plane figure since it is not closed.

## Identification of Plane Figures

Identify whether the following alphabets are plane figures.

A A is not a plane figure. (Not closed)

B B is a plane figure. (Closed)

M M is not a plane figure. (Not closed)

D D is a plane figure. (Closed)

Z Z is not a plane figure. (Not closed)

O O is a plane figure. (Closed)

## Properties of Plane Figures:

1.Plane figures that are completely made of straight lines make angles at the

intersection of two lines.

Number of sides = number of angles

Example:

A triangle has three angles.

A rectangle has four angles.

A pentagon has five angles

Illustration with a hexagon.

2. Any three non collinear points lie on one and only one plane.

3. Plane is a two dimensional figure.

4. Plane figures area and perimeter can be determined.

5. Plane figures do not have volume.

Illustration:

This is a cube whose volume can be determined. But this is not a plane figure.

A three dimensional object has volume whereas plane figures are two dimensional.