Now, I don't know if you misphrased the question but if the pan is x% bigger than half the slice, then it would fit without cutting anything (even if it is 0% bigger and thus equal the size of the pan).

Wait...sorry, it's the area that is compared, thus the diameter won't fit into the pan...right.

The pan is x% bigger than half the area of the pizza (thus I take it you mean the area of the pan).

This is just a guess, cause I'm not that good at math, but let's say this equation would work though, because we need equal slices where the space between them exactly match each slice (so that half the pizza, gets to be full the pizza and thus if x is 100% bigger than half the area of the whole pizza then it would still fit the diameter), let's say the fewest cuts needed are: (x/100)-1.

I'm probably wrong with my equation though, but I think my reasoning is correct; if x is 100% (thus equal the full pizza) then it would fit without any cuts. But if x is smaller than that, then we need to make cuts with equal spacing so that it again fills the entire area of the pan, the cuts should be made so that the spacing + the area of the slizes makes up for 100% of the full area of the pizza.