This document defines and describes various geometric shapes and their properties. It defines line segments, rays, collinear points, and different types of angles such as acute, right, obtuse, straight, and reflex angles. It also defines complementary and supplementary angles. Additionally, it describes properties related to lines such as adjacent angles, linear pairs of angles, vertically opposite angles, corresponding angles formed by a transversal, alternate interior and exterior angles, parallel lines, intersecting lines, and perpendicular lines.
2. (a) Segment: - A part of line with two end points is called a line-
segment.
A line segment is denoted by AB and its length is is denoted by AB.
(b) Ray: - A part of a line with one end-point is called a
ray
3. (c) Collinear points: - If three or more points lie on the same line,
then they are called collinear points, otherwise they are called non-
collinear points.
(d) Angle: - An angle is formed by two rays originating from the same end point.
The rays making an angle are called the arms of the angle and the end-points are
called the vertex of the angle.
4.
5. Acute angle: - An angle whose measure lies
between 0° and 90°, is called an acute angle.
6. Right angle: - An angle, whose measure is equal to 90°, is
called a right angle.
7. Obtuse angle: - An angle, whose measure
lies between 90° and 180°, is called an
obtuse angle.
12. Adjacent angle: - Two angles are adjacent,
if they have a common vertex, common arm
and their non-common arms are on different
sides of the common arm.
13. Linear pair of angles: - If the sum of two
adjacent angles is 180º, then their non-common
lines are in the same straight line and two adjacent
angles form a linear pair of angles.
14. Vertically opposite angles: - When two
lines AB and CD intersect at a point O, the
vertically opposite angles are formed.
15. A transversal is a line that passes through two
lines in the same plane at different points. When
the lines are parallel, as is often the case, a
transversal produces several congruent and
several supplementary angles
16. When two lines are crossed by another line
(which is called the Transversal), the angles in
matching corners are called corresponding
angles.
17. Alternate Interior Angles are created where a transversal crosses two
(usually parallel) lines. Each pair of these angles are inside the parallel
lines, and on opposite sides of the transversal.
18. Alternate Exterior Angles are created where a transversal crosses two
(usually parallel) lines. Each pair of these angles are outside the
parallel lines, and on opposite sides of the transversal.
19. Lines are parallel if they lie in the same plane, and are the
same distance apart over their entire length
20. Two or more lines that meet at a point are
called intersecting lines. That point would be on
each of these lines.
21. Two lines that intersect and form right angles are
called perpendicular lines.
