i always use the fire breath shout first
then flames till we are in melee and then a good sword.
Hm, given that the OP called the troll a snow ape, I'd bet that he neither has a good weapon nor the fire breath shout.
The rocks on the left side always worked well for me. I jump on the rocks, shoot a sneak attack into his back, and then I either pelt him with more arrows until he's dead or summon a bunch of fire atronachs down there to occupy him (while assisting with more arrows).