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**Polygon**– Simple closed figures having three or more line segment are called polygon (or simple closed curve).

**Triangle**– A three sided polygon is called triangle.

**Quadrilateral**– A four sided polygon is called quadrilateral.

**Pentagon**– A five sided polygon is called a pentagon.

**Hexagon**– A six sided polygon is called hexagon.

**Heptagon**– A seven sided polygon is called heptagon.

**Octagon**– A eight sided polygon is called octagon.

**Nonagon**– A nine sided polygon is called nonagon.

**Decogon**– A ten sided polygon is called decogon.

**Regular polygon**– It’s all side are equal & all angles are also equal then it is called a regular polygon.

**Angle**– An angle is a figure formed by two rays with the common initial point. The common initial point is called the vertex of the angle & the rays forming the angle are called its arm.

An angle can also be describe by rotating a ray.

Where OA is initial position and it rotate at center O to final position OB.

Then AOB is an angle, O is vertex and OA and OB are sides of angle.

**Right angle**– If the initial position of a ray is horizontal & it rotates to occupy vertical position then the angle formed is called a right angles($90^0$).

**Straight angle**– If the initial & the final position of a rotating ray are opposite to each other the angle formed is called a straight angle.

**Complete angle**– If a rotating ray after a complete revolution considers with the initial position the angle formed is called a complete angle.

**Adjacent angle**– Two angles are said to be adjacent, if they have a common vertex, arm and other two arms are on the opposite side of the common arm.

**Kinds of angle:-**

**Acute angle**– An angle whose measure is greater than but less than $90^0$ .

**Obtuse angle**-An angle which is greater than a right angle. But less than straight angle ($180^0$ ) is called obtuse angle.

**Reflex angle**– An angle whose measure is more than 1800 but less than $360^0$ , is called reflex angle.

**Right angle**– An angle whose measure is $90^0$ .