Express the sum or difference as a product of sines and/or cosines.
-$\cos ( 6 \theta ) + \cos ( 4 \theta )$
A) $2 \cos ( 5 \theta ) \sin \theta$
B) $2 \cos ( 5 \theta ) \cos \theta$
C) $2 \cos ( 5 \theta )$
D) $2 \sin ( 5 \theta ) \sin \theta$

Question

Quizplus · Accepted Answer

The sum $\cos ( 6 \theta ) + \cos ( 4 \theta )$ can be expressed as a product of cosines using the sum-to-product formula: $\cos A + \cos B = 2 \cos \left( \frac{A + B}{2} \right) \cos \left( \frac{A - B}{2} \right)$. Applying this formula with $A = 6\theta$ and $B = 4\theta$, we get $2 \cos ( 5 \theta ) \cos \theta$.

Express the Sum or Difference as a Product of Sines cos⁡(6θ)+cos⁡(4θ)\cos ( 6 \theta ) + \cos ( 4 \theta )cos(6θ)+cos(4θ)

Express the Sum or Difference as a Product of Sines $\cos ( 6 \theta ) + \cos ( 4 \theta )$