On Fri, Jun 08, 2018 at 02:37:33PM +0900, Stephen J. Turnbull wrote:

My bias is that people who want to program this kind of thing just need to learn about floating point numbers and be aware that they're going to have to accept that

from math import cos, radians cos(radians(90)) 6.123233995736766e-17

is good enough for government work, including at the local public high school.

In Australia, most secondary schools recommend or require CAS calculators from about Year 10, sometimes even from Year 9. Most (all?) state curricula for Year 11 and 12 mandate CAS calculators. Even old-school scientific calcuators without the fancy CAS symbolic maths are capable of having cos(90) return zero in degree mode. It is quite common for high school students to expect cos(90°) to come out as exactly zero. And why not? It's the 21st century, not 1972 when four-function calculators were considered advanced technology :-) To my mind, the question is not "should we have trig functions that take angles in degrees" -- that's a no-brainer, of course we should. The only questions in my mind are whether or not such a library is (1) appropriate for the stdlib and (2) ready for the stdlib. -- Steve