partial sums   2 videos

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  The Sine Addition Formulas

  Trigonometry Advanced Trigonometry

  How to derive the sine of a sum formula.

  cosine of a difference formula the cofunction identities the sine of a sum formula
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  The Double-Angle Formulas

  Trigonometry Advanced Trigonometry

  How to use the sine and cosine addition formulas to prove the double-angle formulas.

  the sine of a sum formula the cosine of a sum formula the sine double angle formula the cosine double angle formula