Tryndamere is op champion but only at late game.So you cant feed at early and mid game.

Runes for attack speed are good for trynda but if you want to change you can.

Masteries must be in offence but rest you can put where you want.

You should buy items exactly like I write them above.After 2nd Bloodthrister you shoud sell Averice Blade and buy Phantom Dancer.Then go to farm your Bloodthristers.After farm and 45 minutes you will have 950-1000 dmg and 2,100 speed.

Flash because everyone love flash and ignite for more dmg.You can change ignite for exhaust.

Pros:
-really big dmg and critical chance
-really over power ultimate
Cons:
-stun when you used utlimate
-silence when you want to use utlimate

Try to not go first in teamfight because you can get stun,silence or other CC and you die fast.

Sry for my English.Good luck!