An object is moving up and down with velocity given by

v$($t$)=195$sin$(7\mathrm{.}8$t$)$

where v is measured in cm per second and t is time in seconds. $($The object is a yo$-$yo$).$ Find the rate of change of height at the instant

t $=0\mathrm{.}5$

seconds. Be accurate to one decimal place. Include units.