Trigonometric functions play a crucial role in the fields of mathematics, physics, engineering, and several other disciplines. They help describe relationships between angles and sides of triangles, particularly in right-angled triangles, making them fundamental in various applications ranging from architecture to astronomy. Trigonometric functions include sine (sin), cosine (cos), tangent (tan), and their reciprocals: cosecant (csc), secant (sec), and cotangent (cot). Each function has specific definitions based on a right triangle or, alternatively, on the unit circle, which provides a more comprehensive way to understand their behavior.