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Trigonometric Addition Formulas

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The trigonometric addition formulas are a set of formulas that express trigonometric functions of sums of angles in terms of the trigonometric functions of the original angles.

Trigonometric addition formulas is a high school-level concept that would be first encountered in a trigonometry course. It is listed in the California State Standards for Trigonometry.

Examples

Double-Angle Formulas: The double-angle formulas are a set of formulas that express trigonometric functions of twice an angle in terms of the trigonometric functions of the original angle.
Half-Angle Formulas: A set of formulas that express trigonometric functions of half an angle in terms of the trigonometric functions of the original angle.

Prerequisites

Cosine: The cosine is the ratio of the length of an angle's adjacent side to the length of the hypotenuse in a right triangle.
Sine: The sine is the ratio of the length of a given angle's opposite side to the length of the hypotenuse in a right triangle.
Tangent: (1) In trigonometry, the tangent of an angle is the ratio of the length of a given angle's opposite side to the length of the angle's adjacent side in a right triangle. (2) In geometry, two figures are said to be tangent to one another if they "just touch".

Classroom Articles on Trigonometry (Up to High School Level)

  • Law of Cosines
  • Trigonometry
  • Law of Sines
  • Unit Circle