GEOMETRY- LINES AND ANGLES
LlNE SEGMENT: A part of a line with two end points is called a line segment. A line segment whose end points are A and B is denoted by .
i. e it has only length but no direction.
A line segment is also a set of infinite points and all the points are in between the end points of the line .
Number of line Segments: If A, B, C, D, E ... are on a line segment , then the number of line segments determained by the ‘n’ points lying on is
Length of a line Segment: The length or measure of a line segment AB is denoted by and it is a positive number showing the distance between A and B.
ComparisIon of line Segments: Two or more line segments can be compared by the virtue of their length. The instruments like ruler, divider, compass can be used to compare, the line segments.
Congruent line Segments: If the lengths of two line segments is same, then they are called as ‘congruent segments’.
i.e. if length of \(\overline {AB} \) = length of \(\overline {CD} \), then it is denoted by \(\overline {AB} \cong \overline {CD} \) where “\(\cong\)” is the symbol of congruency and read as \(\overline {AB} \) is congruent to \(\overline {CD} \)
Measurement of a line Segment : A line segment can be measured by comparing it with a standard segment called a unit segment. The number of times a unit segment is contained in a given segment is called its measure or length.
Example: A line segment \(\overline {PQ} \) is measured by another line segment \(\overline {MN} \) of unit measured
i.e
The basic unit of length in the international system of units (SI) is meter. The other units of length are derived from it as the following :
From the above relation it is noted that
1 cm = 10 mm
1 dm = 10 cm
The instruments like ruler, divider, etc can be used to determine the length of line segments.
The greater lengths like length of claas room, badminton court... etc can be measured by a tape
Betweenness: If A, B and C are any three collinear points and if AB + BC = AC, then we say that B is between A and C. Also if \(\overline {AB} = \overline {BC} \) then B is called mid point of \(\overline {AC} \). Here B is said to be bisector of \(\overline {AC}\)