## History of Trigonometry

The term Trigonometry has been derived from two Greek words, trigonon and metron, which means triangle and to measure respectively. However, until the 16th century, it was mainly about computing the values of the missing parts of the triangle numerically when the other values of the parts were mentioned. Keeping this in mind, let's start with an example to make the concept more clear. The third and the remaining two angles can be calculated if only the length of the two sides of the triangle and the enclosed angle’s measure is given. This distinguishes Trigonometry from geometry as it investigates the qualitative relations. Nevertheless, Trigonometry was considered a part of geometry while it became a separate branch of math during the 16th century.

In a modern sense, Trigonometry started with the Greeks while the first one to make a table of the values of the Trigonometric function was Hipparchus. During his time, these things were expressed in geometric terms like relations between the angles that subtended them and the chords of various forms. Moreover, until the 17th century, the modern symbols of Trigonometric functions were not established.

However, during the 16th century, Trigonometry started to change its character to an algebraic-analytic subject from a geometric discipline as two developments were spurred by the Frenchmen. It was the rise of symbolic algebra and the invention of analytic geometry.

Another aspect of Trigonometry that received great attention was surveying, following which the triangulation’s method was first suggested in 1533 by Gemma Frisius, a Dutch Mathematician. This method was further carried for the first time on a large scale by Willebrord Snell, a Dutchman, who surveyed a stretch of 130 km using around 33 triangles. Keeping these developments in mind, the French government undertook the responsibility to triangulate the entire country under the leadership of Jean Picard, an astronomer. Following this, the survey of the entire continent of India was taken by the British as a means to have an ambitious task. Popularly known by the name of the Great Trigonometric Survey, this survey lasted from 1800 to 1913, which led to the discovery of Mount Everest, the tallest mountain peak on Earth.

Owing to these developments, the scientists from the 18th century diverted their attention to the various aspects of the functions of Trigonometry.

### Origin of the Trigonometry

For the very first time, the idea of ‘sine’ was used in the work by Aryabhatta in A.D 500. He took the word ardha-jya, which was later shortened to jive or jya in the due course. However, when translated, the word jiva became sinus, which meant curve in Latin when translated from the Arabic version. Following this, the word sinus was used as sine in the coming era in mathematical terms throughout Europe. Besides, the first abbreviated notation, known as sin, was termed by an English Professor of astronomy, identified as Edmund Gunter.

The terms ‘tangent’ and ‘ cosine’ originated much later in the time while the need to compute the sine of the complementary angle gave birth to the function of cosine, which was called Kotijya by Aryabhatta. However, Edmund Gunter, the English Professor of astronomy, termed it Cosinus while an English Mathematician, known as Sir Jonas Moore, abbreviated it as ‘cos’ in the year 1674.

Moreover, during the middle ages, Jewish and Arab scholars also played an important role in contributing to the branch. Tangents and cotangents the first table was made by Habash al-Hasib, who also wrote on the topics like astronomy.

Moreover, the main functions based on a right-angled triangle in Trigonometry are Sin, Tan, and Cos.

### Trigonometric Ratios

There are around 6 Trigonometry ratios consisting of sine, cosine, tangent, cosecant, secant, and cotangent, which tells the different possible combinations in a right-angled triangle.

Therefore, the use of Trigonometry in solving a side in right-angled triangles is only possible when the length of the other two sides of the length and angle of a side is already known. For that, one has to choose a ratio that contains the unknown and the given side before using algebra to find the value for the unknown side.

We know in Trigonometry we are going to discuss the relationship between angle and length in right-angled triangles. Let’s first remind ourselves, what we call sides of the right angled triangle.

Observe that above the right-angled triangle ABC is right angled at C. If we consider angle∠B then side AC will be perpendicular, side BC will be called based and side AB is called hypotenuse. Similarly, If we consider angle ∠A then BC will be perpendicular, AC will be considered base and AB will hypotenuse. Among these three, different ratios will give sin, cos, tan, cot, sec, cosec ratios.

### Sin Theta Formula

So now we’ll discuss what sin theta and sin formula are. As we have discussed above, sin is a Trigonometric ratio that is perpendicular/hypotenuse.

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Here x represents the angle which is under consideration.

### Example on Sin x Formula

1. If Cos x = 35, then find the value of Sin x.

Then Find the Value of Sin x.

Solution: We know that, cos θ = BaseHypotenuse

On comparing the given ratio, Base = 3, Hypotenuse= 5.

Now we also know Pythagoras theorem, which says,

(Hypotenuse)² = (Base)² + (Perpendicular)²

⇒ (Perpendicular)² = (Hypotenuse)² - (Base)²

⇒ (Perpendicular)² = 5² - 3²

⇒ (Perpendicular)² = 25 - 9

⇒ (Perpendicular)² = 16

⇒ (Perpendicular)² = 4

Here we are considering only positive signs because the length of the side can’t be negative.

Sin x - 45

Hence this is the required answer.

2. If Cosec x = 67 then Find the Value of Sin x.

Solution: We know that sin x = 1cosec x

Using the above value we have, sin x = 16/7

Hence, sin x = 76

### Brief Overview of Trigonometry

As the name might give you an idea, Trigonometry is all about triangles.

Trigonometry is the branch of mathematics that deals with the relationship between angles and the length (not arc length) of a line made by angle. Whenever we talk about angles, we need to have 2 intersecting lines, through which angle has been made. Adding to that we need one more line on which we’ll measure the length. So, in a nutshell, we need three lines. That’s what “tri” stands for. Now there are many types of triangles we know. Which type of triangle should be? So, the triangle should be right-angled.

If we look deep into it, the system of Trigonometry developed to get angles and distances computed in such fields as mapmaking, astronomy, artillery range finding, and surveying while plane Trigonometry covers problems involving distances and angles in a plane. However, in spherical Trigonometry, it becomes a three-dimensional space.

Nevertheless, Trigonometry is that branch of the system, which helps us determine the unknown or missing sides, lengths, and angles in a given triangle. Specifically, one of the internal angles in the triangle should be 90 degrees. Now we’ll see different types of Trigonometric ratios after taking a peek into its origin.

**1. Who is the Founder of Trigonometry?**

A Greek mathematician, Hipparchus discovered the concept of Trigonometry. He has shown his tremendous work in geography and astronomy.

**2. What are the Primary Trigonometric Functions?**

The Sin function, cosine function and the tangent function are three primary Trigonometric functions.

**3. What is the Formula for Six Trigonometric Functions?**

The formula for six Trigonometric functions are:

Sin x = Perpendicular /Hypotenuse

Cos x = Base / Hypotenuse

Tan x = Perpendicular / Base

Cot x = Base / Perpendicular

Sec x = Hypotenuse / Base

Cosec x = Hypotenuse / Perpendicular

**4. What is Sin Theta?**

Sin theta is a ratio of perpendicular and hypotenuse. In math sin theta or sin function ranges it’s values from -1 to 1. It’s domain is whole real numbers.

**5. What is the Value of x in 1 Sin x Formula?**

When 1 sin theta is equal to 1 then we say that x is equal to π/2. You can see the standard values of sinx formula in following table

x | 0⁰ | 30⁰ | 45⁰ | 60⁰ | 90⁰ |

Sin x | 0 | ½ | 1/√2 | √3/2 | 1 |

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6. What are the sub-branches of Trigonometry?

There are around two different types of sub-branches of Trigonometry, which is further classified into Plane Trigonometry and Spherical Trigonometry. Moreover, plane Trigonometry is for determining distances and height of the angles in a given plane triangle while spherical Trigonometry is about those triangles made on a sphere that is used by astronomers to determine distances in the universe. This method is also adopted by scientists for the same purpose. Spherical Trigonometry originated during the 8th century while mapmakers continue to use it during this time.

7. What are the six basic and important Trigonometric functions?

The six important functions of Trigonometry are sine function, tangent function, cosine function, cosecant function, secant function, and cotangent function while their abbreviations are sin, tan, cos, cosec, sec, and cot respectively. Moreover, these Trigonometric functions can also be described as odd or even while their relationship to sides of a right-angled triangle differs as below:

Sin= opposite side/ hypotenuse

tan= opposite side/ adjacent side

Cos= adjacent side/ hypotenuse

Cosec= hypotenuse/ opposite side

sec= hypotenuse/ adjacent side

cot= adjacent side/opposite side

8. What are the basics of Trigonometry?

Sine, tangent, and cosine are termed as the three basics of Trigonometry because the other functions like secant, cosecant, and cotangent are based and dependent on them to be derived. Most of the concepts in Trigonometry are based on these important functions. Hence, students need to first learn them in detail in order to find the values of given angles. Moreover, Trigonometry is that branch of math whose application is done in real-life on a daily basis and is used broadly by scholars.

9. In which field Trigonometry is applied?

Trigonometry is very helpful in measuring the height of mountains or even finding the distance of rivers by people across the globe. It is applied extensively in various fields like seismology, meteorology, oceanography, astronomy, physical sciences, navigation, acoustics, electronics, marine biology, aviation department, criminology, and much more. Despite the fact that students consider it irrelevant at times while its application in these fields proves that Trigonometry is a vast subject, studied by people to ascertain the value of various things.

5. What was Hipparchus’s contribution to Trigonometry?

The famous astronomer, Hipparchus, was the one who primarily initiated the beginnings of Trigonometry. He is the one to whom the first table of chords is credited and his advances in this field include the calculation of the lunar month, distances of the moon and the sun, the eccentric models of planetary motion, and also the discovery of several things. Moreover, his first known work in Trigonometry was a 12-book work he wrote about the chords in a circle. However, his work does not exist and everything is based on certain speculations. For more answers, check Vedantu for free study materials available on its app and website.