1. A circle with a 7' radius has a circumference of 44' (close enough, anyway)
2. Measure the partial circumference of the curve at the top of the pool.....let's guess it to be 26 feet
3. 26/44= .59 of a full circle.......so, 360 degrees/.59 = 212 degrees
4. If your coping tile is one foot, it will take 26 tiles to complete this curve. Then divide the 212 degrees by 26 tiles and get approx 8 degrees per tile.
5. 8 degrees per tile would be 4 degree cuts on each side of the tile.
6. Grout will have to be considered so your total tile length may be 12.25"
7. That won't be perfect but probably as perfect as you can do with a tile cutter.......it'll look good.
There might be a formula but I don't know it.