Trigonometry pp 123-137 | Cite as

The Addition Formulas

  • I. M. Gelfand
  • Mark Saul


We now come to an important and fundamental property of the sine and cosine functions. If we know the values of sin α and cos α, and also the values of sin β and cos β, then we can calculate the values of \( \sin (\alpha + \beta ),\cos (\alpha + \beta ),\sin (\alpha - \beta ) \), and \( \cos (\alpha - \beta ) \).


Acute Angle Addition Formula Opposite Angle Beautiful Proof Inscribe Angle 
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Copyright information

© I.M. Gelfand 2001

Authors and Affiliations

  • I. M. Gelfand
    • 1
  • Mark Saul
    • 2
  1. 1.Department of MathematicsRutgers UniversityPiscatawayUSA
  2. 2.Bronxville SchoolsBronxvilleUSA

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