Answer
$\frac{1}{6}~second\approx0.1667~second$
Work Step by Step
The time of one full respiratory cycle is the period.
$v=0.85~sin(\frac{\pi}{3}~t)$
$Period=\frac{b}{2\pi}=\frac{\frac{\pi}{3}}{2\pi}=\frac{1}{6}\approx0.1667$
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