(4) We define the binormal vector B(t) to be B(t) = T(t) x N(t). The three unit vectors T(t), N(t) and B(t) forms a frame of reference, called the TNB frame. It is a coordinate system that moves along the curve defined by r(t). This has particular importance in physics and is used, among other applications, in the navigation of spacecraft. Find the vectors T, N and B for r(t) = 4 sinti + 4 costj + 2tk at to = (5) Find the curvature of y = x2 - 3x + 1 at x = 1. (6) A circle is dropped into parabola y = x2. What is the radius of the largest circle that will touch the vertex