How did the minuet and trio create a ternary pattern in Classical symphonies?

In Classical symphonies, the minuet and trio creates a ternary pattern—often referred to as an aba structure—by utilizing a specific sequence of musical sections.12

The form functions as follows:

• Minuet (a): The movement begins with the minuet, a dance piece in moderate triple time that is relatively complete within itself, ending on an authentic cadence.12
• Trio (b): This section follows the minuet. Historically derived from the practice of alternating two minuets, the trio is typically written for a smaller group of instruments and is usually composed in a different key to provide contrast.12
• Minuet (a): The movement concludes with a return to the initial minuet section. This repetition is often indicated by the term da capo ("from the head"), directing the performer to repeat the first section, or it may be written out in full if the composer includes variations.12

This symmetrical arrangement ensures that the movement returns to its original thematic material after the contrasting middle section, defining the classic ternary shape.2