I think the problem is this misunderstands what FPGAs are good at. They're actually very bad (or at least painfully slow) at calculations like your examples. GPUs are good at that.
FPGAs excel in parallelizing very simple operations. One example where FPGAs are good is where you might want to look for a specific string in a network packet. Because FPGAs are electronic circuits you can replicate the "match a byte" logic thousands of times and have those comparisons all run in parallel and the results combined with AND & OR gates into a yes/no decision. (I think the HFT crowd do this sort of thing to preclassify network packets before forwarding candidate packets up to software layers to do the full decision making).
FPGAs excel in parallelizing very simple operations. One example where FPGAs are good is where you might want to look for a specific string in a network packet. Because FPGAs are electronic circuits you can replicate the "match a byte" logic thousands of times and have those comparisons all run in parallel and the results combined with AND & OR gates into a yes/no decision. (I think the HFT crowd do this sort of thing to preclassify network packets before forwarding candidate packets up to software layers to do the full decision making).