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How to find value of cos 20 degree\xa0 |
| Answer» {tex}\\cos 3\\theta = 4{\\cos ^3}\\theta - 3\\cos \\theta \\\\take \\theta =20 \\\\\\frac{1}{2} = 4{x^3} - 3x \\\\8{x^3} - 6x-1=0{/tex}solve the equation | |