Express $\sin 4x + \sin 6x$ as a product of trigonometric functions.
By sum-to-product,
\[\sin 4x + \sin 6x = \boxed{2 \sin 5x \cos x}.\]
By sum-to-product,
\[\sin 4x + \sin 6x = \boxed{2 \sin 5x \cos x}.\]
The final answer is $The final answer is: \[2\sin(5x)\cos(x).\]$. I hope it is correct.