## Algebra and Trigonometry 10th Edition

$A=20~millimeters~of~mercury$ It represents the variation of the pressure around 100 millimeters of mercury. That is, the pressure goes from 80 to 120 millimeters of mercury.
In the function: $y=y_0+A~cos~Bt$, $|A|$ is the amplitude. In $P=100-20~cos~\frac{8\pi t}{3}$ the amplitude is: $A=|-20|=20$