Product-to-Sum Formulas

Proposition (Product-to-Sum Formulas) The following formulas hold for all angles and where the functions are defined.  

Example (Product-to-Sum Formulas) Find the exact value of

    Solution. We have,












Example (Product-to-Sum Formulas) Prove the trigonometric identity:

    Solution. We have,
    











Example (Product-to-Sum Formulas) Prove the trigonometric identity:

    Solution. We have,
    

















Example (Product-to-Sum Formulas) Solve the equation

    Solution. We have,















where is any integer
    
    
Example (Product-to-Sum Formulas) Solve the equation

    Solution. We have,















where is any integer

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Cite this as:
Product To Sum Formulas
Published by Library of Math -- Online math organized by subject into topics.
Written by Smith, David A.
http://www.libraryofmath.com/product-to-sum-formulas.html