Chapter 10.28

Sum and difference identities


What You'll Learn

Apply sum and difference identities to evaluate sine, cosine, and tangent of angle combinations
Recognize how to break complex angles into sums or differences of special angles
Use Pythagorean identities to find missing trigonometric ratios from given values
Convert between radian and degree measures to simplify identity applications
Verify factored trigonometric expressions by applying sum and difference formulas

What You'll Practice

1

Simplifying expressions using sine and cosine sum and difference identities

2

Evaluating tangent of non-standard angles without a calculator

3

Proving trigonometric identities by expanding sum and difference formulas

4

Finding exact values by converting radians to degrees and applying special triangles

5

Determining trig ratios in different quadrants using reference angles

Why This Matters

Sum and difference identities are essential tools for solving complex trigonometric equations in calculus, physics, and engineering. You'll use these formulas to simplify expressions, prove identities, and evaluate exact valuesskills that appear in standardized tests and advanced STEM courses.

This Unit Includes

8 Video lessons
Practice exercises

Skills

Sum Identities
Difference Identities
Trigonometric Identities
Special Triangles
Reference Angles
Exact Values
Radian Conversion
Identity Proofs
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