The phrase "are so predetermined" is correct and usable in written English.
It can be used to describe something that is established or decided in advance, often implying a lack of freedom or choice.
Example: "The outcomes of the experiment are so predetermined that any variation in results seems unlikely."
Alternatives: "are so preordained" or "are so fixed".
A key difficulty is that this plot is so predetermined there is little point in seeing it through to the end.
For the possible causes and meanings of anxiety are so varied that any one predetermined answer is sure to be often wrong.
It's difficult to get a straight answer to the question of whether or not our sleep preferences are predetermined because there are so many factors that play a role genetics, biology, environment, lifestyle, even our mental health.
Plans are so advanced that each tree and boulder, all salvaged from the old site, has a predetermined home on the new one.
The outcome of the presidential contest appears so predetermined that some commentators have compared Mr. Putin's campaign to ads during Soviet times to "Fly Aeroflot," the state-owned airline, as if there were a choice.
In fact, the group says the system appears to be so rigged that "the outcomes of most Congressional races are effectively predetermined long before the election takes place".
What made the decision so galling for liberals and moderates, however, was that its reasoning was so sketchy and unconvincing that it seemed like a transparent mask for a predetermined political result.
He said: "It makes no sense to go through a process requiring research and testimony when the final numbers are predetermined so early out of City Hall.
The equation in Figure 2e illustrates the linearisation process whereby a spectrum of exponentials convolved with the input function are predetermined so as to allow the linear solution for the blood-perfusion weighting terms given by α i.
