A wave travels along a string, and its position in millimeters is described by $h\left(t\right)=15(2\cos t+1)$, for $t\ge 0$, where $t$ represents time in seconds. Determine the velocity of the wave, $v\left(t\right)=h^{\prime }\left(t\right)$.

• A. $v\left(t\right)=30\sin t\text{ mm/s}$
• B. $v\left(t\right)=-30\sin t\text{ mm/s}$
• C. $v\left(t\right)=15{\sec }^{2}t\text{ mm/s}$
• D. $v\left(t\right)=-30{\csc }^{2}t\text{ mm/s}$

Answer: (B)