Important Formulas: Understanding Elementary Shapes | Mathematics (Maths) Class 6 PDF Download

Measurement of Line Segment

• A line segment is defined as a segment of a line that is fixed in place. This enables the measurement of a line segment.
• The length of a line segment is the distance between its endpoints.
• When comparing the lengths of line segments, a graduated ruler and a divider are used. These methods give accurate length distance.
• Also, we can compare the two line segments by observation or with the help of trace paper. But, both the methods have very little accuracy and we can’t trace the lengths every time.

Angles – ‘Right’ and ‘Straight’

• An example of an angle is when the hand of a clock shifts from one location to another.
• A right angle is used to turn from north to east.
• A full turn is made by turning in the same direction by two straight angles (or four right angles).
• The angle for one revolution is called a complete angle.
• One revolution's angle is a full angle.
• A protractor is used to calculate the size of an angle in degrees.
• A 1/4 revolution is a right angle, whereas a 1/2 revolution is a straight angle.

• From above,
  Clock 1 represents 1/2 of revolution or 2 right angles.
  Clock 2 represents 1/4 of revolution or 1 right angle, and
  Clock 3 represents 3/4 of revolution or 3 right angles.
• A right angle is 1/4 a revolution and a straight angle is 1/2 a revolution.
• Protractor is an instrument used to measure the size of an angle in degrees.
• The measure of a right angle is 90^o and hence that of a straight angle is 180^o.
• An angle is said to be acute if its measure is less than that of a right angle and is said to be obtuse if its measure is more than that of a right angle but is less than a straight angle.
• Sea-saw, rooftop, opening book, etc. are examples of an acute angle.
• House, desk for book reading, etc. are examples of an obtuse angle.
• A reflex angle is larger than a straight angle.
• Two intersecting lines are perpendicular if the angle between them is 90^o.
• The perpendicular bisector of a line segment is perpendicular to the line segment that divides it into two equal parts.

Triangles can be classified as follows based on their angles

• An acute angle is an angle smaller than a right angle.
• An obtuse angle is one that is greater than a right angle but smaller than a straight one.
• A reflex angle is more than twice as large as a straight angle.

Triangles can be classified as follows based on the lengths of their sides:

Polygons are named based on their sides:

Quadrilaterals are further classified with reference to their properties:

Faces, Edges, and Vertice

• Each side of the cube is a flat surface called a flat face (or simply a face). 
• Two faces meet at a line segment called an edge. 
• Three edges meet at a point called a vertex.

Prism

• The triangular prism has a triangular base, whereas the rectangular prism has a rectangular base.