How much accuracy does a high school trig student need?
To grasp the concept? Not much.
But I remember being an AA graduate in surveying and having a Structural engineer with a Masters join the company and doing a bunch of mapping calculations using pi as 3.14
Took me weeks to fix everything...
I don'k know. My HP-48 gives me sines, cosines, and tangents out to 12 decimal places. Any of your cheap scientific calculators that I've ever seen will give you better than 6 decimal places. I find Dr. Wildberger's remarks about accuracy suspicious.
6 significant digits