I need help solving a few equations.

1) The voltage V in a certain electric circuit as a function of the time t (in s) is given by V=2.0sin178tcos178t. How fast is the voltage changing when t=3.0 ms?

2) Find the derivative of the given function. V=(6tan)(^-1s)

3) Find the slope of the line tangent to the curve of y=sinx/2x, where x=0.10

4) Find the derivative of the function. y=(sin^2)(4xcos3x)