# How do you graph y = -3 cos x?

For a general cosine trigonometric function of form $y = a \cos b x$, a represents the amplitude ie the maximum displacement from the x-axis, and the period, ie distance on the x-axis for 1 complete cycle, is given by $\frac{2 \pi}{b}$
So in this case, a=-3 and period is $2 \pi$