Rewrite the following as a product of trigonometric functions.
-$\cos 11 ^ { \circ } - \cos 24 ^ { \circ }$
A) $- 2 \sin 17.5 ^ { \circ } \sin \left( - 6.5 ^ { \circ } \right)$
B) $- 2 \sin 17.5 ^ { \circ } \cos \left( - 6.5 ^ { \circ } \right)$
C) $- 2 \cos 17.5 ^ { \circ } \sin \left( - 6.5 ^ { \circ } \right)$
D) $- 2 \cos 17.5 ^ { \circ } \cos \left( - 6.5 ^ { \circ } \right)$

Question

Quizplus · Accepted Answer

The formula for the difference of cosines is $\cos A - \cos B = -2 \sin \left( \frac{A+B}{2} \right) \sin \left( \frac{A-B}{2} \right)$. Applying this to $\cos 11^\circ - \cos 24^\circ$, we get $-2 \sin 17.5^\circ \sin(-6.5^\circ)$.

Rewrite the Following as a Product of Trigonometric Functions cos⁡11∘−cos⁡24∘\cos 11 ^ { \circ } - \cos 24 ^ { \circ }cos11∘−cos24∘

Rewrite the Following as a Product of Trigonometric Functions $\cos 11 ^ { \circ } - \cos 24 ^ { \circ }$