Chapter 4.5, Problem 90E

(a)

To determine

To find: The period of the function.

Answer to Problem 90E

The period of the function is $\frac{6}{5}$ seconds.

Explanation of Solution

Given information:

The expression is

  $p=100-20\cos \frac{5\pi t}{3}$

Calculation:

Calculate the period model,

  $\begin{array}{c}Period=\frac{2\pi }{\left(\frac{5\pi }{3}\right)}\\ =\frac{6\pi }{5\pi }\\ =\frac{6}{5}\end{array}$

Therefore, the period model is $\frac{6}{5}$ seconds.

(b)

To determine

To find: The number of heart beats per minute.

Answer to Problem 90E

The number of heart beats per minute is 50.

Explanation of Solution

Given information:

The expression is

  $p=100-20\cos \frac{5\pi t}{3}$

Calculation:

As in $\frac{6}{5}$ seconds 1 heartbeat is completed,

Calculate the heartbeats completed in 60 seconds.

  $\begin{array}{c}=\frac{60}{\frac{6}{5}}\left(1\right)\\ =10\times 5\\ =50\end{array}$

Therefore, the number of heart beats per minute is 50.