6. Find the derivative of y = 4cos(x) 7. The depth, y in feet, of water in Boston harbor is given in terms of t, the number of hours since midnight by y = 5 + 4.9cos Find dy/dt. What does dy/dt represent, in terms of 6 water level? For 0s t s 24, when is dy/dt zero? Explain what it means (in terms of water level) for dy/dt to be zero. 8. Find the derivative of y = In(In(x)) 9. Find the derivative of y = arcsin(x ) + arccos(2x)