Can you use Trip in combination with Whirlwind Attack?
I understand that the rules for Whirlwind Attack state "When you use the Whirlwind Attack feat, you also forfeit any bonus or extra attacks granted by other feats, spells, or abilities." But what is a bonus? The rules of trip simply state "You can attempt to trip your opponent in place of a melee attack." while Whirlwind says "make one melee attack at your highest base attack bonus against each opponent within reach." There are no bonuses or extra attacks involved, and you're not using any feats, spells, or abilities - You're simply using a melee attack to make a combat maneuver.
So, theoretically, would you be able to substitute the melee attacks made during your Whirlwind with trip attempts?