# Introduction to Basic Geometry and Angles on Parallel Lines

#### In this post, we will discuss Basic Geometry and Angles on Parallel Lines that will help you solve questions from the geometry section of quantitative aptitude and help you save time in SSC Exam

Basic Geometry is a branch of mathematics that deals with the study of shapes, figures and its properties. Basic Geometry is one of the oldest sciences, it goes back to Pythagoras, Euclid and etc who have contributed in the field of geometry.

Geometry is a vast subject. Since you all are preparing for SSC Exams, in this post we will discuss Basic Geometry and Angles on Parallel Lines that will help you solve questions in SSC Exams.

In SSC Exams, Questions are asked from the Plain Geometry section of Basic Geometry.

### What is a Plain Geometry?

Plain geometry is a part of basic geometry that deals with plain figures such as Circles, Triangles, Quadrilaterals - Square, Triangle, Rectangle, Parallelogram, Trapezium, Rhombus etc.

### Basic Geometry: Point

A point is the simplest geometrical shape that can be drawn and it has no sides. It is the simplest of all the geometrical shapes. A point is represented by a dot and it is always named with an upper case letter.

### Basic Geometry: Line

A line is described by its length. It has got infinite length but no breadth. A line is made up of infinite points and it extends itself to infinity. Two arrows are drawn at the ends to show the infinite extension of the line.

### Basic Geometry: Line Segment

A line segment is a part of a line. It falls between the two given defined points. A line segment has two end points and it is also made up of infinite points.

### Basic Geometry: Ray

A ray is a collection of points that begins at one point and extends itself to infinity. The difference between a ray and a line is that a ray has a starting point.

Example: Sun Rays

### Basic Geometry: Angles

The angular distance between two rays or lines that are connected to the common point is called as an angle.

### Based on their measurements, angles can be classified into different categories:

Acute angle: An acute angle is an angle which is less than 90 degrees.

Right angle: A right angle is an angle which is exactly 90 degrees.

Obtuse angle: An obtuse angle is an angle which is greater than 90 degrees but less than 180 degrees.

Straight angle: A straight angle is an angle which is exactly 180 degrees.

Reflex angle: A reflex angle is an angle which is greater than 180 degrees but lesser than 360 degrees.

Complete angle: A complete angle is exactly 360 degrees.

Basic Geometry: Supplementary angles
Supplementary angles are those angles which sum up 180 degrees.

Basic Geometry: Complementary angles
Complementary angles are those angles which sum up to 90 degrees.

Basic Geometry: Parallel lines

Lines which are parallel in nature to each other and distance between them remains constant at all times are called as Parallel Lines.
AB//CD

Basic Geometry: Transversal lines

Transversal line is a line that cuts the two parallel lines.
When a transversal cuts a pair of parallel lines, there are many angles that are formed.

Basic Geometry: Properties of Angles on Parallel Lines

Basic Geometry: Property 1

Parallel lines which are cut by a transversal line enable angles to be formed on the straight line that sums up to 180 degrees.

Basic Geometry: Property 2

Parallel lines which are cut by a  transversal line, angles that are formed on the opposite sides are equal. These angles are also called as vertical angles.

Basic Geometry: Property 3

Parallel lines which are cut by a transversal line, angles that are formed on the corresponding sides are equal.

Basic Geometry: Property 4

Parallel lines which are cut by a transversal line, angles that are formed on the alternate sides are equal.

There are two types of alternate angles.

Basic Geometry: Property 5

When Parallel lines are cut by a transversal line there are a few indirect pair of supplementary angles that are formed. These indirect pair of supplementary angles are of two types.

1.  Interior indirect Supplementary Angles which are on the same side.

2.  Exterior indirect Supplementary Angles which are on the same side.

Hope this post - Introduction to Basic Geometry and Angles on Parallel Lines have been of help to you while preparing for SSC CGL 2017 as questions from geometry section often appear in these competitive exams.

Do write in the comment section below on how this post has helped you solve basic geometry and angles on parallel lines questions asked in mock tests for SSC CGL. Also, download free questionnaire for practice!

Stay tuned for our next blog.