Chapter 6 - 6.4 - Graphs of Sine and Cosine Functions - 6.4 Exercises - Page 464: 7

$Amplitude=\frac{3}{4}$ $Period=4$

If $y=a~cos(bx)$ $Amplitude=|a|$ $Period=\frac{2\pi}{b}$ $y=\frac{3}{4}~cos(\frac{\pi x}{2})$ $Amplitude=|\frac{3}{4}|=\frac{3}{4}$ $Period=\frac{2\pi}{\frac{\pi}{2}}=2\pi\frac{2}{\pi}=\frac{4\pi}{\pi}=4$