Question

math help.

Answer 1

how do i do this?

Answer 2

Make use of the following formula:
\[\large \cos (A-B)=\cos A \cos B+\sin A \sin B\]

Answer 3

i think the first choice should read: \[y=\cos x \cos 3\color{red}\pi+\sin x \sin3\color{red}\pi\]
... that would make it correct

Answer 4

The graph is of cos x, with a phase shift of -3 radians. Therefore the graph is of the function cos (x - 3).
\[\large \cos (x-3)=\cos x \cos 3+\sin x \sin 3\]