One learns trigonometry in high school/secondary school and either forgets it if one continues onto a career less mathematical or, possibly, uses it extensively in their work, as do engineers and physicists.
As a field of study in mathematics however, it seems that trigonometry is mostly "solved", at least it seems so for the familiar trigonometry in $\mathbb{R}^2$. Is this true, or are there still interesting questions that deal with trigonometry or, perhaps, generalizations of it?
In Āryabhaṭa's sine table the jya values or 'modern values' still have to be fully computed. So the Āryabhaṭa's computational method is still being researched.