removing ceramic floor tile

[Fishboy]

Brad,
I'm laying slate tile on my concrete walkway that takes a 90 degree arch from the front door to the driveway. I would like to cut the tiles on wedges to have them take this 90 degree arch, but am in a bind to figure an easy way to lay out the cuts to get the angles right. Are there any tricks to smoothly and cleanly take a 90 degree turn with tile?

Thanks for any advice,
Brian

Mahalo nui loa,
Brian and Mary
Lynnwood, WA\Discovery Harbour