Chapter 14 Trigonometric Graphs, Identities, and Equations - 14.2 Translate and Reflect Trigonometric Graphs - 14.2 Exercises - Quiz for Lessons 14.1-14.2 - Page 922: 6

See below.

The amplitude and period of a graph $y=a\cos (bx)$ or $y=a\sin(bx)$ can be obtained by (if $a,b$ are non-zero): amplitude: $|a|$, period: $\frac{2\pi}{|b|}$. Hence here the amplitude is: $|3|=3$ The period: $\frac{2\pi}{|\pi/2|}=4$.