I've found it easy to defeat the T Rex at the last level by equipping the knife to enable
turok to run faster, and running to the far side of the of the area from which you
originally started to pick up the rocket launcher. You'll have to weave around the giant
crates in the courtyard to evade the t Rex, but once you reach the far side of the
courtyard there will be a rectangular giant crate that has the rocket launcher sitting on
the left side of it. To kill the T Rex quickly I suggest not using the automatic targeting
for the launcher, but simply blind fire until the T Rex falls on its side. Then equip the
knife, run up to the T Rex, and do the final killing move. Which is pressing the right
trigger button when the icon appears.