This is a substantial oversimplification of course (there are many more factors involved than how fast the ball is growing in the visual field), but I think the point is clear enough. I doubt there's any trigonometry happening in the brain's circuitry; it seems much more plausible to me that the brain is really good at remembering how it felt in previous circumstances, recognizing how those remembered circumstances relate to the current one, and trying to adjust.
As I understand it, this is actually a significant debate in cognitive science, philosophy of mind, and related fields. One prominent proponent of a view like the one I've expressed here, that the brain doesn't require or use heavy math to do things like catch flying objects but rather acquires the ability over time through experience, is John Searle. He is known for using the example of his dog's ability to catch a ball that's bounced off a wall when discussing and arguing against theories of mind that propose that all unconscious processes must be following algorithms or rules (like running through computations to figure out how to catch a ball). Here's a quote of his from the BBC program Horizons (quote found in "New Technologies in Language Learning and Teaching", issue 532, on page 37 [1]):
If my dog can catch a ball that's bounced off the wall, that may be
just a skill he's acquired. The alternative view (the pro-AI view)
would say: "Look, if the dog can catch the ball it can only be
because he knows the rule: go to the point where the angle of
incidence equals equals the angle of reflection in a plane where the
flatness of the trajectory is a function of the impact velocity
divided by the coefficient of friction" - or something like that.
Now, it seems to me unreasonable to think that my dog really *knows*
that. It seems to me more reasonable to suppose he just learns how
to look for where the ball is going and jumps *there*. And a lot of
our behavior is like that as well. We've acquired a lot of skills,
but we don't have to suppose that, in order to acquire these skills,
the skills have got to be based on our mastery of some complex
intellectual structure. For an awful lot of things, we just *do* it.
[1] https://books.google.com/books?id=fWQhj0HVCbUC&pg=PA37&lpg=P...