Question 1009712
 A particle moves along the number line so that it's directed distance from the origin at any given time t is  given by s(t) = -2 sin t 
 Find the velocity(the rate of change of s) of the particle at t = {{{pi}}} seconds.
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v(t) = s'(t) = -2cos(t)
v(pi) = -2cos(pi) = -2 units/second