To prove the second formula using the first, start by rewriting the dot product in the exponential of the first formula in terms of known quantities, specifically magnitudes and angles. Define the q-vector along the z-hat direction to simplify calculations. Next, express the measure in spherical coordinates to facilitate the proof. This approach allows for a clearer transition from the first to the second formula. Following these steps will lead to a successful demonstration of the relationship between the two formulas.