You can put this solution on YOUR website! General solution of cos3x+cos^3x=0
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cos(3x) = 4cos^3(x) - 3cos(x)
From "Half Angle Formulas" on Wikipedia
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4cos^3(x) - 3cos(x) + cos^3(x) = 0
--> 5cos^3(x) - 3cos(x) = 0
cos*(5cos^2 - 3) = 0
cos(x) = 0
x = n*pi, n = any integer
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5cos^2 = 3
cos(x) = sqrt(3/5)
x = acos(sqrt(0.6))
