Find curvature given r (t) = e^t*cost i + e^t*sint j.

There are two formulas but I was told to avoid using the formula that does not involve the cross product when no value for the parameter t is given.

Formulas:

1. K = ||r'(t) X r"(t)||/||r'(t)||^3

2. K = ||T' (t)||/||r'(t)||

Which formula is "easier" to apply in this case and/or in most cases? I was told to apply formula (1) for polynomials. What about for problems involving e^t, lnx and trigonometric functions?