Use the Sum-To-Product Formulas to Select the Sum or Difference $\cos 3 \theta + \cos 6 \theta$

question 27

Multiple Choice

Use the sum-to-product formulas to select the sum or difference as a product.
$\cos 3 \theta + \cos 6 \theta$

• A) \(2 \cos \frac { 9 \theta } { 2 } \cos \left( - \frac { 3 \theta } { 2 } \right)\)
• B) \(2 \cos \frac { 9 \theta } { 2 } \sin \left( - \frac { 3 \theta } { 2 } \right)\)
• C) \(2 \cos \frac { 9 \theta } { 2 } \cos \left( \frac { 3 \theta } { 2 } \right)\)
• D) \(2 \cos \left( - \frac { 9 \theta } { 2 } \right) \cos \frac { 3 \theta } { 2 }\)
• E) \(2 \cos \frac { 9 \theta } { 2 } \sin \left( \frac { 3 \theta } { 2 } \right)\)

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