Question

\[\sec^2 (\pi/7) + \sec^2 (3\pi/7) + \sec^2(5\pi/7)\]

Answer 1

@rational

Answer 2

@amistre64

Answer 3

I was thinking of making a cubic just for the sake for it.

Answer 4

\[= \sec^2(2\pi/7) + \sec^2(4\pi / 7) + \sec^2 (6\pi/7)\]Seems better this way.

Answer 5

Yeah, I think I can make a cubic now...