= 8. r(t) [sin 3t cos 3t 3t], find (a) the arc length from (-1,0,1.5) to (0,1,6), (b)the unit tangent vector at point (0,1,6), (c) the velocity, acceleration vectors at point (0,1,6), (d)the curvatureat point (0,1,6). (16%)