Trigonometry: Foundations Quiz

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12 Questions

What is the meaning of the word 'trigonometry' based on its Greek origin?

Measurement of triangular corners

In a right triangle, which angle is usually taken as the fixed point for measuring other angles?

Vertex angle

What is the sum of the two complementary angles in a right triangle when one side is horizontal?

90 degrees

Which angle in a triangle is referred to as the 'opposite angle' to a particular side?

Obtuse angle

What is the term used to describe an angle that is adjacent to a specific side in a triangle?

Adjacent angle

Which type of triangle has one angle equal to 90 degrees?

Right triangle

What does the Pythagorean theorem state?

The square of the hypotenuse is equal to the sum of the squares of the other two sides.

Which trigonometric function is defined as the ratio of the opposite side to the hypotenuse?


In what discipline is trigonometry used to calculate the orbits of planets and moons?


What is the reciprocal of the cosine function?


Which trigonometric function connects the adjacent side to the hypotenuse?


Why is trigonometry essential in architecture?

To visualize and calculate angles, heights, and distances in designs.

Study Notes

Trigonometry: Foundations of Circular Geometry

Trigonometry is a branch of mathematics concerned with relationships between angles and lengths of sides in triangles and functions based on these ratios. It has applications in many fields such as physics, engineering, computer graphics, signal processing, statistics, probability, and geometry.

The word "trigonometry" comes from the Greek words "tri," meaning three, and "gonia," meaning angle. This name reflects its origins in measuring the shape of triangular corners of land parcels using simple geometry.

Basic Concepts

Triangle Sides and Angles; Measuring Length and Angle

A triangle is defined by having three edges (or sides) and three vertices (corners). Two of the sides are connected with each other by two angles; their sum equals 90 degrees when one side is horizontal. These two angles are called complementary angles.

In trigonometry, we measure the angles of a right triangle relative to a fixed point known as the vertex, which is usually one of the right angles. We can have three types of angles: acute, obtuse, and reflex.

For example, if A, B, and C are the angles of a triangle in order around it (clockwise), then angle A is called the opposite angle to side BC, while angle B is called the adjacent angle to side AC. Similarly, angle C is called the hypotenuse to side AB.

Right Triangle Formulas

A right triangle is a triangle with one angle equal to 90°. In this case, the length of the hypotenuse (the longest side opposite the right angle) is given by the Pythagorean theorem, which states: the square of the hypotenuse is equal to the sum of the squares of the other two sides.

Here's an example formula: If c² = a² + b² Then: c = √(a² + b²)

where c represents the length of the hypotenuse, and a and b represent the lengths of the other two sides.


Trigonometric functions, also called circular functions because they apply to all angles measured in radians, provide a way to relate the coordinates of a point in Cartesian space to the polar coordinates of the same point.

There are six basic trigonometric functions, each mapping points on the unit circle to a real number:

  1. Sine: sine(θ) = opposite side / hypotenuse
  2. Cosine: cosine(θ) = adjacent side / hypotenuse
  3. Tangent: tangent(θ) = opposite side / adjacent side
  4. Secant: secant(θ) = 1 / cosine(θ)
  5. Cosecant: cosecant(θ) = 1 / sine(θ)
  6. Cotangent: cotangent(θ) = 1 / tangent(θ)

These functions describe periodic patterns and give us access to the properties of geometric shapes.


Trigonometry is essential in various disciplines, including physics, engineering, architecture, astronomy, earth sciences, geographic mapping, navigation, medicine, music theory, and more. Here's how:

  • Physics: Trigonometry helps understand motion, energy, and forces.
  • Engineering: Trigonometry is critical in many areas of engineering, such as structural analysis, design of mechanical systems, and control theory.
  • Architecture: Trigonometry helps architects visualize and calculate angles, heights, and distances.
  • Astronomy: Trigonometry is used to calculate the orbits of planets, moons, and other celestial bodies.
  • Earth Sciences: Trigonometry is essential in surveying, geodesy, and geophysics.
  • Geographic Mapping: Trigonometry helps create accurate maps and measure distances.
  • Navigation: Trigonometry is used to calculate the distance between two points and to determine the speed and direction of a moving object.
  • Medicine: Trigonometry is used in imaging techniques such as sonar and x-ray imaging.
  • Music Theory: Trigonometry is used to understand frequencies and vibrations.

In conclusion, trigonometry is a fundamental branch of mathematics that lies at the heart of many scientific and engineering applications. Its practical use spans a wide range of disciplines, from measuring the height of mountains to understanding the orbits of planets and the vibrations of musical instruments. Trigonometry's applications are vast, and this is just a brief overview of its importance.

Test your knowledge on the foundational concepts of trigonometry, including triangle sides and angles, right triangle formulas, trigonometric functions, and real-world applications in various fields like physics, engineering, architecture, astronomy, and more.

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