Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
This build is only for 3vs3. If you know how to properly play Tryndamere you can destroy any squishy enemy and escape with your spells/ult. Whirlwind is good for getting to buffs when the other team is not expecting it. With life steal and bloodlust you can solo dragon rather early game. Controlling a lane and switching to jungle can easily get you higher levels than the opponents. After you have boots try getting agility pots for more crit and AS. Finish up with the rest of the item list ,but towards mid/late game keep Agi pot on at all times.