# Trigonometry I – What is Trigonometry with Trigonometric Ratios for SSC and Other Exams

### Trigonometry may appear to be complex but is simple if approached the right way. Read on to understand what is trigonometry along with an explanation of trigonometric ratios.

What is
Trigonometry? Trigonometry is a branch of mathematics that deals with the length
of the side of a triangle and the angles in a triangle. Trigonometry is not a
very common topic in competitive exams, however it is asked in a few exams like
SSC CGL and SSC CHSL where it is given good weightage. Therefore it makes it
essential for us to study this topic. Trigonometric ratios are one of the
fundamental pillars of trigonometry. We will start our series on trigonometry
by discussing the different trigonometric ratios.

### What is Trigonometry- Different Systems for Measuring an Angle

There are 3
different ways to measure an angle.
1.   Sexagesimal or
English System: Degrees
In this system the angle is measured in terms of degrees. As per this system, one right angle constitutes 90°, one degree constitutes
60’ and one minute is 60’’.

2.   Centesimal or
In this system the angle is measure in terms of grade. The
root word of this system is ‘cent’ which means 100, so in this system one right
angle is equal to 100g (g here stands for grades), one grade is
equal to 100’ and each minute is equal to 100’’.
3.   Circular System:
In this system the angle is measure in terms of radians. One
radian (1c) is the angle subtended at the centre of a circle by an
arc of length equal to the radius of the circle.
On comparing the three systems we can say-

The above relationship can be used to convert an angle in one
system to an angle in the other system.
1c = 1 x 180/p = (180 x 7)/22 = 570 17’ 45’’
So remember-

### What is Trigonometry- Relationship between Radius, of the Length Arc and the Angle Subtended at the Centre

Before we move ahead to trigonometric ratios, let us discuss
the relationship between the radius, length of the arc and angle subtended at
the centre, in a circle.
Look at the diagram below, where we consider a circle with
radius ‘r’, centre ‘O’ and an arc of length ‘l’.
The length of the arc is the product of the
radius and the angle subtended at the centre. (The angle is in terms if

### Trigonometric Ratios

Trigonometric ratios are the simply the ratios of
different sides of a right angled triangle with respect to acute angle. So for
trigonometric ratios we simply take two sides and get their ratios, and based
on the different pair of sides we choose, we get different trigonometric
ratios.
Here we have a right angled triangle, which had a 900
angle at the vertex A. We know the side opposite to the right angle is called the Hypotenuse,
the initial line is the Base of the triangle and
the third side is the perpendicular. We also have an angle
θ at the vertex B. With respect to this angle we are going to consider the
various trigonometric ratios.

The
side opposite to θ is the perpendicular and the side adjacent to θ is the base.

Stay tuned for more on trigonometry and till then don’t stop practicing!