2. Let r(t) be a curve of constant speed defined on the interval [-7, 7]. If the unit tangent vector of r(t) at any point is given by T(t) = (sint, cost) and the curve length of r(t) is 47, then the value of r' (7 /4) is A. (V2, - V2) B. (-V2/2, V2/2) C. (V2, 0) D. (V2/2, V2/2) E. (V2, V2)Given that unit tangent vecher T ( it) = 7'( 1 14 ) = z, 527 ( option : E )