Cosine Function

beginnertrigonometrybasic ratios

Defines cosine as ratio in a right triangle

The Formula

cos(θ) = adjacent / hypotenuse

Variables & Symbols

θ

Angle

adjacent

Side adjacent to angle θ

hypotenuse

Longest side

When to Use This Formula

  • Right triangle calculations
  • Vector projections
  • Physics problems

Worked Examples

Example 1

Problem:

adjacent=4, hypotenuse=5, find cos(θ)

Solution: cos(θ) = 0.8

Step-by-Step:

1

cos(θ) = 4/5 = 0.8

Common Mistakes to Avoid

  • Confusing adjacent with opposite

Real-World Applications

1

Engineering

2

Computer graphics

3

Physics

Practice Problems

Problem 1: cos(60°) = ?

Show Answer

Answer: 0.5

Related Formulas

sine definition

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tangent definition

View Formula →

Tags:

trigonometrycosineratios

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