Trigonometry+Polynomials=Trigonomials
Geometry
Level
5
\[\large 8x^3-6x+1 = 0\]
If \(a\), \(b\) and \(c\) are the roots of the equation above, find the value of \(\cos^{-1} a + \cos^{-1} b + \cos^{-1} c\) in degrees.
If you think that roots exist outside \([-1, 1]\), write 272 as your answer.
by
Sharky Kesa