Vectors functions

[ggxoxo]

Can someone please help me with these questions?

1-At time t, a particles has coordinates (6t, t^2+4). Find the unit vector along the tangent to the path when t=4

2-The position vector of a particle is given by r(t)=10sin2t i + 5cos5t i. Find the cosine of the angle between its direction of motion at t=0 and t=pi/6

3- Find the unit tangent vector of the curve r= 5(cosx i+ sinx j)

4- The velocity of a particle is given by v= (t-3) j, t>0. Show that the path of this particle is linear.

Thank you!!!