Advanced Angle Relationships and Trigonometric Identities

This section expands on angle relationships and introduces important trigonometric identities, building upon the concepts from the previous page.

The page begins by exploring angles that differ by 180°:

• sin$180° + α$ = -sin α
• cos$180° + α$ = -cos α
• tan$180° + α$ = tan α

It then discusses angles that sum to 360°, which is particularly useful when working with angles in the fourth quadrant:

• sin$360° - α$ = -sin α
• cos$360° - α$ = cos α
• tan$360° - α$ = -tan α

Highlight: Understanding these angle relationships is crucial for solving problems involving angles in different quadrants of the unit circle.

The document then introduces one of the most fundamental trigonometric identities:

Definition: The Pythagorean identity states that sin²α + cos²α = 1 for any angle α.

This identity is the basis for many other trigonometric relationships and is extensively used in trigonometric proofs and problem-solving.

Additional relationships between trigonometric ratios are presented:

• tan²α + 1 = sec²α
• 1 + cot²α = csc²α

These identities are crucial for simplifying complex trigonometric expressions and solving advanced trigonometric equations.

Example: To prove that tan²θ + 1 = sec²θ, start with the Pythagorean identity and divide both sides by cos²θ.

The page provides a solid foundation for understanding the interrelations between various trigonometric functions, setting the stage for more advanced topics in trigonometry.

Trigonometric Formulas for Compound Angles and Double Angles

This page delves into more advanced trigonometric formulas, focusing on compound angles $sum and difference of angles$ and double angles. These formulas are essential for solving complex trigonometric problems and are widely used in calculus and physics.

The section begins with the formulas for the sum of angles:

• sin$α + β$ = sin α cos β + cos α sin β
• cos$α + β$ = cos α cos β - sin α sin β
• tan$α + β$ = $tan α + tan β$ / $1 - tan α tan β$

Following this, the formulas for the difference of angles are presented:

• sin$α - β$ = sin α cos β - cos α sin β
• cos$α - β$ = cos α cos β + sin α sin β
• tan$α - β$ = $tan α - tan β$ / $1 + tan α tan β$

Highlight: These compound angle formulas are fundamental in trigonometry and have numerous applications in physics and engineering.

The page then introduces double angle formulas:

• sin$2α$ = 2 sin α cos α
• cos$2α$ = cos²α - sin²α = 2cos²α - 1 = 1 - 2sin²α
• tan$2α$ = 2tan α / $1 - tan²α$

Example: To find sin 60°, you can use the double angle formula with α = 30°: sin 60° = 2 sin 30° cos 30° = 2 * $1/2$ * $√3/2$ = √3/2

The document also covers half-angle formulas, which are derived from the double angle formulas:

• sin$α/2$ = ±√$(1 - cos α$ / 2)
• cos$α/2$ = ±√$(1 + cos α$ / 2)
• tan$α/2$ = ±√$(1 - cos α$ / $1 + cos α$) = sin α / $1 + cos α$ = $1 - cos α$ / sin α

These formulas are particularly useful when dealing with angles that are half of common angles, such as 22.5° or 15°.

The page concludes with an introduction to the sine and cosine laws, which are crucial for solving non-right triangles:

Definition: The Law of Sines states that for any triangle ABC, a/sin A = b/sin B = c/sin C, where a, b, and c are the lengths of the sides opposite to angles A, B, and C respectively.

Definition: The Law of Cosines states that for any triangle ABC, a² = b² + c² - 2bc cos A, where a is the side opposite to angle A, and b and c are the other two sides.

These laws are fundamental in trigonometry and have wide-ranging applications in surveying, navigation, and physics.

Trigonometric Values for Common Angles and Reference Table

This final page provides a comprehensive reference table of trigonometric values for common angles, which is an invaluable resource for quick calculations and problem-solving in trigonometry.

The table includes values for sine, cosine, and tangent for angles from 0° to 360° at key intervals:

• 0°, 30°, 45°, 60°, 90° $first quadrant$
• 120°, 135°, 150°, 180° $second quadrant$
• 210°, 225°, 240°, 270° $third quadrant$
• 300°, 315°, 330°, 360° $fourth quadrant$

Highlight: Memorizing these common angle values is crucial for efficient problem-solving in trigonometry and related fields.

Some notable values include:

Example:

• sin 30° = 1/2
• cos 60° = 1/2
• tan 45° = 1
• sin 90° = 1
• cos 180° = -1
• tan 0° = 0

The table also includes special cases where functions are undefined, such as tan 90° and tan 270°.

Vocabulary: "Undefined" in trigonometry typically occurs when a function's denominator equals zero, resulting in division by zero.

This reference table is particularly useful for:

1. Quickly solving trigonometric equations
2. Verifying calculator results
3. Understanding the behavior of trigonometric functions across different quadrants
4. Recognizing patterns in trigonometric values

By providing these values, the table reinforces the concepts of periodicity and symmetry in trigonometric functions. It also helps in visualizing the unit circle, a fundamental concept in trigonometry that relates circular motion to the trigonometric functions.

Quote: "Trigonometry is a fundamental tool in mathematics, physics, and engineering. Mastering these common angle values opens doors to understanding more complex mathematical and scientific concepts." - Anonymous mathematician

This comprehensive table serves as a capstone to the trigonometric concepts and formulas presented in the previous pages, providing a quick and reliable reference for a wide range of trigonometric calculations.

Trigonometric Fundamentals and Angle Relationships

This page introduces essential trigonometric concepts and formulas, focusing on complementary and supplementary angles and their trigonometric relationships.

The document begins by presenting the basic trigonometric ratios of sine, cosine, and tangent. These fundamental ratios are defined in terms of the sides of a right-angled triangle.

Definition: Sine $sin$ is the ratio of the opposite side to the hypotenuse, cosine $cos$ is the ratio of the adjacent side to the hypotenuse, and tangent $tan$ is the ratio of the opposite side to the adjacent side.

The page then delves into the concept of angle reduction to the first quadrant, which is crucial for solving trigonometric problems involving angles greater than 90°.

Highlight: Understanding angle reduction is key to simplifying complex trigonometric calculations.

Complementary and supplementary angles are thoroughly explained, along with their trigonometric relationships:

1. Complementary angles sum to 90°. Their trigonometric ratios are related as follows: sin$90° - α$ = cos α cos$90° - α$ = sin α tan$90° - α$ = 1/tan α
2. Supplementary angles sum to 180°. Their trigonometric ratios are: sin$180° - α$ = sin α cos$180° - α$ = -cos α tan$180° - α$ = -tan α

Example: If angle A is 30°, its complement is 60°. Therefore, sin 30° = cos 60°, and cos 30° = sin 60°.

The page concludes with additional trigonometric functions such as secant, cosecant, and cotangent, providing a comprehensive overview of all six trigonometric functions.