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Actually, if cos5@ = 1.'. cos5@=1
So 5@=pi, 2pi, 3pi, 4pi, 5pi ...
let the roots be 1,a,a,b,b thenKFunk said:cos<sup>2</sup>(2π/5)cos<sup>2</sup>(4π/5) = 1/16
Get some simultaneous stuff happening with summing roots and you should get some exact values.