(1) only needs to write "0, 30, 45, 60, 90, 180", and everything else can be deduced by inductive formula.

(2) It is essentially two right-angled triangles "1, 1, √2" and "1, √ 3,2".

(3) Draw this right triangle, one by one, several times more, remember.

(4) At the high school/university stage, most mathematical formulas/concepts are "first understood, then memorized", so don't rely on so-called formulas, because there are too many formulas/concepts to memorize.