That looks correct.
a point is moving along the graph of the given function such that dx/dt is 2 cm/sec. find dy/dt for the given values of x
y=cosx
i ended up changing this to dy/dt=-sinx*2
x = pi/6 -> dy/dt = -1
x = pi/4 -> dy/dt = -squareroot(2)
x = pi/3 -> dy/dt = -squareroot(3)
sorry if this is a little messy jw if my awnsers are correct for each x value