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**Line and Angles:**

The distance between the endpoints of a line segment is the** **length of the line segment.**Length of a line segment:**

The distance between the endpoints of a line segment is the length of the line segment. The length of a line segment can be measured accurately using a ruler and a divider.**Complete angle:**

An angle of measure 360**°** is called a complete angle.

One quadrant = ¼ (Complete angle) = 1/4 x 360°90° = Two quadrants = 1/2

(Complete angle) = 1/2 x 360° = 180°

Three quadrants = 3/4 (Complete angle) = 3/4 x 360° = 270°**Right angle:**

An angle that measures** **90° is called a right angle. A right angle makes a quarter revolutions.**Straight angle:**

An angle that measures 180° is called a straight angle. A straight angle makes a half revolution.**Acute angle:**

An angle that measures less than 90° is called an acute angle.**Obtuse angle:**

An angle that measures** **more than 90° and less than 180° is called an obtuse angle.**Reflex angle:**

An angle that measures** **more than 180° is called a reflex angle.**Intersecting lines:**

Two lines that meet each other at a single point are called intersecting lines.**Perpendicular lines:**

Two lines that intersect each other at right angles are said to be perpendicular to each other.**Bisector of a line segment:**

A bisector of a line segment is a line that divides the line segment into two equal parts.

Perpendicular bisector of a line segment:

The perpendicular line that divides a line segment into two equal parts is called the perpendicular bisector of the line segment.**Two Dimensional Figures**

The closed figure formed by joining three line segments end-to-end is called a triangle. Each line segment forms a side of the triangle.**Scalene Triangle:**

A triangle is called a scalene triangle if all the three sides are of unequal length.**Isosceles Triangles:**

A triangle is called an isosceles triangle if two of its sides are of equal length.**Equilateral Triangle:**

A triangle is said to be an equilateral triangle if the lengths of all of its sides are equal.**Acute-Angled Triangle:**

If all the angles of a triangle are less than 90°, then the triangle is called an acute-angled triangle.**Right-Angled triangle:**

If one of the angles in a triangle is a** **right angle, then the triangle is called a right-angled triangle.**Obtuse-Angled Triangle:**

If one of the angles in a triangle is an obtuse angle, then the triangle is called an obtuse-angled triangle.**Parallelogram:**

A parallelogram is a four-sided figure in which the opposite sides are parallel to each other and are of equal length. In a parallelogram, the diagonals need not be equal in length.**Rectangle:**

A rectangle is a type of parallelogram that has opposite sides equal in length and parallel to each other. Its diagonals are equal in length. A rectangle has** **four right angles.**Square:**

A square is a type of parallelogram in which all the four sides are equal in length. Its diagonals are equal in length. A square has four right angles.**Rhombus:**

In a rhombus, all the sides are equal in length, and the **opposite sides **are parallel to each other. Its diagonals are not equal in length. Also, the opposite angles are equal to each other.**Trapezium:**

A trapezium has one pair of sides parallel to each other. The other two sides are not parallel to each other.**Polygon:**

A polygon is a closed figure with three or more than three sides.**Three Dimensional Shapes**

Solid figures have three dimensions - length, breadth and height.

Eg: A ball, a brick, an ice cream cone and a can.

**Face**

The flat surface of a solid shape is called a face.

**Edge**

An edge is a line segment two faces of a solid shape meet.

**Vertex**

A vertex of a solid shape is a point where three or more edges meet. A cuboid has** **6 faces, 12 edges and 8 vertices. Prisms and pyramids are named after their bases. The base of a prism can be of any polygonal shape.

There are** **5 faces, 9 edges and 6 vertices in a**Triangular prism**

There are 4 faces, 6 edges and 4 vertices** **in a triangular pyramid.

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