46 lines
2.0 KiB
Markdown
46 lines
2.0 KiB
Markdown
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---
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title: Trigonometric Identities
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---
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# Trigonometric Identities
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*Trigonometric Identities* are equalities that involve trigonometric functions. Trigonometric functions are functions of an angle that relate the angles of a triangle to the lengths of its sides (e.g. sine, cosine, and tangent). *Trigonometric Identities* are true for every value of the variables where both sides of the equality are defined.
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Whenever expressions involving trigonometric functions need to be simplified, *Trigonometric Identities* are very useful.
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## List of Trigonometric Identities
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- Angle Addition Formulas
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- Double-Angle Formulas
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- Half-Angle Formulas
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- Harmonic Addition Theorem
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- Mollweide's Formulas
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- Morrie's Law
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- Multiple-Angle Formulas
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- Newton's Formulas
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- Prosthaphaeresis Formulas
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- Simpson's Formulas
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- Sine-Tangent Theorem
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- Trigonometric Addition Formulas
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- Trigonometric Power Formulas
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- Trigonometric Series Formulas
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- Trigonometry Angles
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- Trigonometry Angles--0
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- Trigonometry Angles--Pi/2 - Pi/32
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- Wallis Cosine Formula
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- Wallis Formula
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- Wallis Sine Formula
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- Weierstrass Substitution
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- Werner Formulas
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#### Cosines and Sines Around the Unit Circle
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![Cosine and Sine are the Unit Circle](https://upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Unit_circle_angles_color.svg/640px-Unit_circle_angles_color.svg.png?1507763902323)
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## Other Resources
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- <a href='http://mathworld.wolfram.com/topics/TrigonometricIdentities.html' target='_blank' rel='nofollow'>Wolfram MathWorld - Trigonometric Identities</a>
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- <a href='http://mathworld.wolfram.com/TrigonometryAnglesPi3.html' target='_blank' rel='nofollow'>Wolfram MathWorld - Trigonometry Angles--Pi/3</a>
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- <a href='http://mathworld.wolfram.com/30-60-90Triangle.html' target='_blank' rel='nofollow'>Wolfram MathWorld - 30-60-90 Triangle</a>
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- <a href='https://www.wikiwand.com/en/List_of_trigonometric_identities' target='_blank' rel='nofollow'>Wikipedia - List of Trigonometric Identities</a>
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- <a href='https://www.wikiwand.com/en/Trigonometric_functions' target='_blank' rel='nofollow'>Wikipedia - Trigonometric Functions</a>
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