Chapter 8.2, Problem 82E

(a)

To determine

To calculate: The monthly sales for $\text{February }2015$, when the monthly sales S for next 2 years is forecasted as $S=23.1+0.442t+4.3\sin \frac{\pi t}{6}$.

$T\left(t\right)=98.6+4\cos \frac{\pi t}{36}\text{ 0}\le t\le 18$

(b)

To determine

To calculate: The monthly sales for $\text{February }2016$, when the monthly sales S for next 2 years is forecasted as $S=23.1+0.442t+4.3\sin \frac{\pi t}{6}$.

$T\left(t\right)=98.6+4\cos \frac{\pi t}{36}\text{ 0}\le t\le 18$

(c)

To determine

To calculate: The monthly sales for $\text{September }2015$, when the monthly sales S for next 2 years is forecasted as $S=23.1+0.442t+4.3\sin \frac{\pi t}{6}$.

$T\left(t\right)=98.6+4\cos \frac{\pi t}{36}\text{ 0}\le t\le 18$

(d)

To determine

To calculate: The monthly sales for $\text{September }2016$, when the monthly sales S for next 2 years is forecasted as $S=23.1+0.442t+4.3\sin \frac{\pi t}{6}$.

$T\left(t\right)=98.6+4\cos \frac{\pi t}{36}\text{ 0}\le t\le 18$