## Questions and Answers

What does the cosine function represent in a right triangle?

Adjacent over hypotenuse

Which trigonometric function is equivalent to \( \frac{1}{sin(\theta)} \)?

Cosecant (csc)

If \( \sin(\theta) = \frac{3}{5} \), what is \( \cos(\theta) \)?

( \frac{3}{4} )

What is the reciprocal of cotangent (cot) function?

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In a right triangle, which ratio does the tangent function represent?

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What does the sine function represent in a right triangle?

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What is the period of the cosine function?

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Which trigonometric identity relates sine and cosine to 1?

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What are the coordinates of a point on the unit circle with angle θ?

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What is the inverse of the tangent function?

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How does the sine function behave with respect to periodicity?

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Which identity involves the double angle for cosine?

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## Study Notes

## Trigonometry: The Language of Angles and Triangles

Trigonometry, from the Greek words "trigonon" (triangle) and "metron" (measure), is a branch of mathematics that deals with angles and the relationships between the sides and angles of triangles. In this exploration, we'll dive into some fundamental concepts and applications of trigonometry, focusing on right triangles, trigonometric functions, identities, and inverse trigonometric functions, all within the context of the unit circle.

### Right Triangle Trigonometry

A right triangle is one with a 90-degree (or π/2 radian) angle at its vertex. The Pythagorean theorem, (a^2 + b^2 = c^2), provides the relationship between the lengths of the three sides of a right triangle (labeled as (a), (b), and (c), with (c) being the hypotenuse). Trigonometry introduces the six basic trigonometric ratios, which are ratios of the sides of a right triangle:

- Sine ((\sin)): (\frac{opposite}{hypotenuse})
- Cosine ((\cos)): (\frac{adjacent}{hypotenuse})
- Tangent ((\tan)): (\frac{opposite}{adjacent})
- Cosecant ((\csc)): (\frac{1}{sin})
- Secant ((\sec)): (\frac{1}{cos})
- Cotangent ((\cot)): (\frac{1}{tan})

These ratios are defined for a specific angle in a right triangle and are denoted by the corresponding letter followed by the angle enclosed in parentheses. For example, (\sin(\theta)) denotes the sine of angle (\theta) in a right triangle.

### Trigonometric Functions

Trigonometric functions are continuous functions that represent the relationship between the angles and sides of a right triangle. They are also periodic functions with specific periods and characteristics.

- Sine: (\sin(x + 2\pi k) = \sin(x)) for all integers (k)
- Cosine: (\cos(x + 2\pi k) = \cos(x)) for all integers (k)
- Tangent: (\tan(x + \pi) = -\tan(x))

### Trigonometric Identities

Trigonometric identities are relationships between different trigonometric functions of the same or different angles. Some fundamental identities include:

- Pythagorean identity: (\sin^2(\theta) + \cos^2(\theta) = 1)
- Substitution: (\sin(\pi/2 - x) = \cos(x)), (\cos(\pi/2 - x) = \sin(x)), (\tan(\pi/2 - x) = \cot(x))
- Double angle: (\sin(2x) = 2\sin(x)\cos(x)), (\cos(2x) = 2\cos^2(x) - 1 = 1 - 2\sin^2(x))

### Unit Circle

The unit circle is a circle with a radius of 1 and center at the origin of the coordinate plane. It is a convenient tool for visualizing and understanding trigonometric functions. The coordinates of a point on the unit circle are given by ((\cos(\theta), \sin(\theta))). By knowing the value of (\theta), we can find the corresponding coordinates of the point on the unit circle.

### Inverse Trigonometric Functions

Inverse trigonometric functions, also known as arcsin, arccos, arctan, etc., are the inverse operations of the basic trigonometric functions. They are used to find the angle associated with a given trigonometric ratio.

- Arcsin: (\arcsin(x) = \theta), where (\sin(\theta) = x)
- Arccos: (\arccos(x) = \theta), where (\cos(\theta) = x)
- Arctan: (\arctan(x) = \theta), where (\tan(\theta) = x)

Trigonometry is a widely applicable field, from calculating the height of a building from its shadows, to measuring waves in physics, to understanding sound and music. The concepts presented above provide the foundation for understanding the many facets of this fascinating subject and its numerous applications.

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