Trignometry - Relationships Among Trigonometric Fuctions

Relationships Among Trigonometric Functions

This table presents key relationships between the fundamental trigonometric functions \(\sin \alpha\), \(\cos \alpha\), \(\tan \alpha\), and \(\cot \alpha\). Understanding these relationships helps in simplifying expressions and solving trigonometric equations.

Key Relationships

sin α cos α tan α cot α
sin α   ± \(\sqrt{1 - \cos^2 \alpha}\) ± \(\frac{\tan \alpha}{\sqrt{1 + \tan^2 \alpha}}\) ± \(\frac{1}{\sqrt{1 + \cot^2 \alpha}}\)
cos α ± \(\sqrt{1 - \sin^2 \alpha}\)   ± \(\frac{1}{\sqrt{1 + \tan^2 \alpha}}\) \(\cot \alpha \tan \alpha\)
tan α \(\frac{\sin \alpha}{\sqrt{1 - \sin^2 \alpha}}\) ± \(\frac{\sqrt{1 - \cos^2 \alpha}}{\cos \alpha}\)   \(\frac{1}{\tan \alpha}\)
cot α ± \(\frac{\sqrt{1 - \sin^2 \alpha}}{\sin \alpha}\) \(\frac{\cos \alpha}{\pm \sqrt{1 - \cos^2 \alpha}}\) \(\frac{1}{\tan \alpha}\)  

Terminology

  • Trigonometric Functions: Functions relating angles of a triangle to ratios of its sides, including sine (\(\sin\)), cosine (\(\cos\)), tangent (\(\tan\)), and cotangent (\(\cot\)).
  • Nested Functions: Expressions where one trigonometric function appears inside another, such as \(\tan^2 \alpha\) or \(\sqrt{1 - \cos^2 \alpha}\).
  • Positive and Negative Signs (\(\pm\)): Indicates that depending on the quadrant of angle \(\alpha\), the function value can be positive or negative.

Applications

  • Used to simplify complex trigonometric expressions in algebra and calculus.
  • Helpful in solving trigonometric equations by converting between functions.
  • Applied in physics and engineering problems involving waveforms, oscillations, and circular motion.
  • Essential in computer graphics for rotations, transformations, and modeling.
  • Useful in signal processing for analyzing phase and amplitude relationships.
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