Hi the question is as following,

The displacement of a body after time t is given as s = tsint + cost. Calculate its velocity and acceleration values at t = 3

(an: -2.970; -1.413)

I used equation ds/dt = v to find the derivative which is

v = tcost + sint -sint

but when i put t = 3 to the equation can't get the right answer, I thought it would be the problem of the derivation but I can't find which goes wrong.

(Crying)