Rectilinear Figure

What is rectilinear figure?

A plane figure whose boundaries are line segments is called a rectilinear figure. A rectilinear figure may be closed or open.

Polygon: A closed plane figures whose boundaries are line segments is called a polygon. The line segments are called its sides and intersection of consecutive sides is called a vertex. In general, a figure bounded by more than four line segments is called a polygon. A polygon is given a special name according to the number of sides it has.

For example:

1. Pentagon:

$Pentagon Polygon$

It’s a 5 sided polygon. The sides are PQ, QR, RS, ST and TP.

2. Hexagon:

$Polygon Hexagon$

It’s a 6 sided polygon. The sides are PQ, QR, RS, ST, TU and UP.

3. Heptagon:

$Polygon Heptagon$

It’s a 7 sided polygon. The sides are PQ, QR, RS, ST, TU, UV and VP.

4. Octagon:

$Polygon Octagon$

It’s a 8 sided polygon. The sides are PQ, QR, RS, ST, TU, UV,VW and WP.

5. Nonagon:

$Polygon Nonagon$

It’s a 9 sided polygon. The sides are PQ, QR, RS, ST, TU, UV,VW, WX and XP.

5. Decagon:

$Polygon Decagon$

It’s a 10 sided polygon. The sides are PQ, QR, RS, ST, TU, UV,VW, WX, XY and YP.

What is diagonal of a polygon?

A line segment joining any two consecutive vertices of a polygon is called a diagonal of a polygon.

$What is Diagonal of a Polygon?$

Here, the pentagon PQRST, the diagonals are PR, PS, QS, QT and RT.

Interior and exterior angles of a polygon:

The angle between any two consecutive sides of a polygon is called an interior angle of a polygon.

$Interior and Exterior Angles of a Polygon$

Here, QPT, PQR, QRS, RST and STP are the interior angles.

If one side of a polygon is produced, the angle of the extended side makes with the next side of the polygon is known as an exterior angle of the polygon.

$Interior and Exterior Angles of a Polygon Image$

Here, APQ, BQR, CRS, DST and ETP are the exterior angles.

At every vertex, the interior angle and the exterior angle form a linear pair, i.e., the sum of the interior angle and the exterior angle equals 180 degree. For example, QPT + APQ = 180°.

Convex polygon:

If the interior angles of a polygon are less than 180 degree, the polygon is known as convex polygon.

$Convex Polygon$

Here, PQRSTU is a convex hexagon.

Non convex polygon:

If atleast one interior angle of a polygon is more than 180 degree, the polygon is known as a non convex polygon.

$Nonconvex Polygon$

Here, PQRSTUV is a non convex heptagon as reflex TUV 180°.

Equilateral polygon:

A polygon whose all sides are equal is called an equilateral polygon.

Equiangular polygon:

A polygon whose all angles are equal is called an equiangular polygon.

Regular polygon:

A polygon whose all sides and all angles are equal is called a regular polygon.

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