Use a Sum or Difference Identity to Find the Exact $$\cos 9 ^ { \circ } - \cos 33 ^ { \circ }$$

question 265

Multiple Choice

Use a sum or difference identity to find the exact value.
- $$\cos 9 ^ { \circ } - \cos 33 ^ { \circ }$$

• A) \(- 2 \sin 21 ^ { \circ } \cos \left( - 12 ^ { \circ } \right)\)
• B) \(- 2 \cos 21 ^ { \circ } \sin \left( - 12 ^ { \circ } \right)\)
• C) \(- 2 \cos 21 ^ { \circ } \cos \left( - 12 ^ { \circ } \right)\)
• D) \(- 2 \sin 21 ^ { \circ } \sin \left( - 12 ^ { \circ } \right)\)