A parametrized curve is given by: r(t)= (3cos(t), 5sin(t), 4cos(t))
1. at t= π/4 , determine the vector r→'(t) X r→''(t). (First derivate crossed with second derivate)
2. At t= π/4 , find the unit tangent and the principal normal vectors T(t) and N(t).