If the unit of the rate constant is \( \text{mol} \, (\text{dm}^{-3} \text{s}^{-1}) \), the order of the reaction would be ____________.
Explain the construction of a spherical wavefront by using Huygens' principle.
The slope of the tangent to the curve \( x = \sin\theta \) and \( y = \cos 2\theta \) at \( \theta = \frac{\pi}{6} \) is ___________.