Show that cos(π/7) - cos(2π/7) + cos(3π/7) = 1/2.
(In reply to
Solution by Nick Hobson)
Very clever.
I had difficulty understanding the part about the coefficient of z^6. However, I understand this step better by considering the seven seventh roots of -1 as vectors on the Argand plane, pulling in equal amounts at regular angular intervals, with the net total force then being zero.
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Posted by Charlie
on 2004-12-06 21:50:53 |
re: Solution
