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Precalculus: Sum and Difference Formulas in Trigonometry

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Terms in this set (7)

  • How can you find cos 15° using sum or difference formulas?

    Rewrite 15° as 45° - 30°, then use cos(45° - 30°) = cos 45° cos 30° + sin 45° sin 30°.

  • What is the tangent difference formula?

    tan(α - β) = (tan α - tan β) / (1 + tan α tan β)

  • How can sum and difference formulas be used in reverse?

    To express sums or differences of products like cos 40° cos 80° - sin 40° sin 80° as a single cosine of a sum or difference.

  • How can you find exact values of trigonometric expressions using sum and difference formulas?

    By expressing angles as sums or differences of known angles and applying the formulas.

  • How can sum and difference formulas help solve trigonometric equations?

    By rewriting expressions as sums or differences of angles to simplify and solve.

  • What is the sine difference formula expressed using sine and cosine?

    sin(α - β) = sin α cos β - cos α sin β

  • What is the cosine difference formula expressed using sine and cosine?

    cos(α - β) = cos α cos β + sin α sin β