The primary solution is defined as a solution that fulfills a specific equation or a set of equations. The provided expression comprises two factors, and the accurate identification of the primary solution can be achieved by examining each component individually. - Option (1) is erroneous because it represents a basic sinusoidal function. The expression \( (5 + 3 \sin \theta) \) is a constituent of the equation but might not be the primary solution. - Option (2) is accurate as it includes a cosine function, which is integral to the solution's formation.