Talk:Sine of Integer Multiple of Argument/Formulation 5

No mistake.

When $k = 4r + 1$ then $\paren {\sin \frac {k \pi} 2} = 1$

When $k = 4r + 3$ then $\paren {\sin \frac {k \pi} 2} = -1$

When $k = 2r$ then $\paren {\sin \frac {k \pi} 2} = 0$. --Robkahn131 (talk) 21:00, 22 September 2023 (UTC)

See comment under Formulation 7. We could build a lemma, and transclude it as needed. Hence we have an edge. --prime mover (talk) 22:33, 22 September 2023 (UTC)