# CLASS-4POLYGONS

POLYGON -

A simple closed curve made of line segments only is called a polygon.

Rectangle, square, triangle, circle… are all polygons.

TYPES OF POLYGONS -

1. TRIANGLE :-

A polygon which is made of three line segments is called a triangle.

A triangle has three sides, three angles and three vertices (or corners).

Sides =>  Segment AB, BC, CA

Vertices => Points A, B, C

Angles => Angles A, B, C

A simple closed figure bounded by four line segments is called a quadrilateral.

A quadrilateral has four sides, four angles, four vertices (or corners) and two diagonals.

The line segment that joins the two opposite vertices of a quadrilateral is called a diagonal.

4 Sides  => AB, BC, CD, DA

4 Angles => A, ∠B, ∠C, ∠D

2 Diagonals => AC, BD

3. RECTANGLE :-

A quadrilateral whose opposite sides are equal and all four angles are equal is called a rectangle.

The longer side of the rectangle is called length while the shorter side of the rectangle is called width or breadth.

Each angle of the rectangle measures 90°. The diagonals are equal.

4 Sides => AB, BC, CD, DA

2 Equal sides =>  AB, DC and AD, BC

2 Equal parallel sides are =>  AB ∥ DC  & AD ∥ BC

4. SQUARE :-

A quadrilateral having all its sides equal and all its angles equal is called a square.

Each angle of the square measures 90°. The diagonals are equal.

4 Sides are equal => AB = BC = CD = DA

5. CIRCLE :-

A circle is a simple closed curve with a center.

TYPES OF TRIANGLES : (BASED ON LENGTH OF THEIR SIDES) -

1. SCALENE TRIANGLE :-

A triangle of whose all sides are unequal, is called a scalene triangle.

Here, AB ≠ BC ≠ CA

2. ISOSCELES TRIANGLE :-

A triangle having two of its sides equal (congruent) is called an isosceles triangle.

Here, AB = AC, but BC ≠ AB, and BC ≠ AC

3. EQUILATERAL TRIANGLE :-

A triangle in which all the three sides are equal (congruent) is called an equilateral triangle.

Here, AB = BC = CA