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Understanding Trigonometry from Scratch: Sine, Cosine, and Tangent

Trigonometry is a particularly deep and widely applicable field within mathematics.

Originating in ancient Greek astronomy and surveying, it is now an indispensable tool in fields ranging from modern engineering and physics to information technology.

This article will first explain the basic concepts of “What is trigonometry?”, then look at how it is used in various situations, and finally explain the benefits of learning trigonometry.

1. What is Trigonometry?


Trigonometry is a set of functions that express the relationship between angles and side lengths in a right-angled triangle. The most well-known of these are sine (sin), cosine (cos), and tangent (tan).

- Definition in a Right-Angled Triangle

In a right-angled triangle, trigonometric functions are defined by the ratios of the sides opposite, adjacent, and hypotenuse to a given acute angle. For example, for an angle θ:
  - sin θ = Opposite ÷ Hypotenuse
  - cos θ = Adjacent ÷ Hypotenuse
  - tan θ = Opposite ÷ Adjacent

- Periodicity and Wave Modelling

Trigonometric functions have periodicity and are well-suited to representing waves and oscillations. Sine waves and cosine waves are used to model a wide range of phenomena, including the analysis of sound, light, and electrical signals, as well as the movement of celestial bodies and the patterns of climate change.

- Relationship to Complex Numbers

Euler's formula (e^(iθ) = cos θ + i sin θ) shows how trigonometric functions behave on the complex plane and plays an important role in advanced mathematical and engineering fields such as signal processing and Fourier transforms.

Thus, trigonometry goes beyond simply being about the ratios of sides in a triangle; it is a fundamental tool for describing waves and periodic phenomena in nature and technology.

2. In What Situations is Trigonometry Used?


Due to its universal properties, trigonometry is used in a wide range of fields. Here are some representative examples:

- Physics

In mechanics, waves, and electromagnetism, trigonometric functions are used to analyse oscillations, periodic motion, and wave propagation. Examples include the motion of a pendulum, sound waves represented as sine waves, and interference phenomena of light.

- Engineering & Control Engineering

It is important for modelling and simulating actual phenomena, such as vibration analysis of structures, rotational motion of mechanical parts, and AC analysis of electrical circuits. In signal processing and communications, it is indispensable for the Fourier transform, a technique used to decompose complex signals into frequency components.

- Computer Graphics

Trigonometric functions are used to transform coordinates and angles when generating visual effects, animations, and rotating or transforming 3D models. This enables realistic image representation and object movement.

- Surveying & Astronomy

Trigonometry has been used since ancient times to measure distances and angles and remains an important tool for mapmaking and calculating the positions of celestial bodies.

- Economics & Statistics

Trigonometric functions can be used to analyse seasonal data and periodic trends. For example, sine waves and cosine waves can be incorporated into models for time series prediction and cycle analysis.

These examples demonstrate that trigonometry is not just a part of mathematics; it is a powerful language that expresses the underlying universal laws of nature and engineering technology.

3. What are the Benefits of Learning It?


Learning trigonometry has significant benefits in many areas.

- Deepening Mathematical Thinking

Trigonometry fosters abstract mathematical thinking through concepts such as angle, periodicity, and amplitude. This deepens understanding of more complex mathematical concepts and analytical techniques.

- Improving Application Skills in Engineering & Physics

It is an essential foundational knowledge for real-world modelling and simulation, signal processing, and 3D graphics. Engineers and researchers can enhance their ability to describe difficult phenomena with simple formulas.

- Improving Problem-Solving Skills & Creativity

By learning how to capture data and phenomena within a framework of periodicity, you develop an approach to seeing problems from different perspectives. This makes it easier to solve complex problems.

- Cross-Disciplinary Application

Trigonometric knowledge can be used in a wide range of fields, including physics, engineering, computer graphics, and even music and economic analysis. Therefore, the skills you learn can directly contribute to a diverse range of careers.

- Enhancing Logical & Visual Expression

Through graphs and waveforms, you develop the ability to understand phenomena not only mathematically but also visually, enhancing your data insight and presentation skills.

In Conclusion


Trigonometry is a mathematical tool that developed from the ratios of sides in a right-angled triangle and is used to express periodic phenomena, waves, and rotational motion.

By learning trigonometry, you develop the ability to understand often-overlooked everyday phenomena and the beautiful patterns behind nature and technology. Start by thoroughly mastering the basics and gaining experience by analyzing phenomena using formulas and graphs, and your horizons will expand even further.

 If you want to learn trigonometry, we recommend this book (access here).

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