Answer:
[tex]\cos(11x)[/tex]
Step-by-step explanation:
Given
[tex]\cos 5x\ \cos 6x- \sin\ 5x \sin 6x[/tex]
Required
Express as a single function
In trigonometry, we have:
[tex]\cos(A + B) = \cos A\cos B - \sin A \sin B[/tex]
By comparison, we have
[tex]\cos(5x + 6x) = \cos 5x\cos 6x - \sin 5x \sin 6x[/tex]
[tex]\cos(11x) = \cos 5x\cos 6x - \sin 5x \sin 6x[/tex]
