cosx cannot = 0 ; x cannot = pi/2 or 3pi/2
sinx=0 or sinx-2cos^3x=0
+-sqrt(1-cos^2x) - 2cos^3x=0
+-sqrt(1-cos^2x) = 2cos^3x
*square both sides to remove radical
1-cos^2x = 4cos^6x
I don't know how to solve this equation, can someone please provide me with a link to read how to solve this equiation?