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giải phương trình:
1) 2cos^2 x+2cos^2 2x = 2 cos^2 3x -3 =4cos4x(2sin2x +1)
2) ( 2sinx +1)(3cos4x +2sinx -4) + 4cos^2 x= 3
3) 32cos^6 x - cos6x = 4
4) tan^2 x(1-sin^3 x) + cos^3 x = 0
1) 2cos^2 x+2cos^2 2x = 2 cos^2 3x -3 =4cos4x(2sin2x +1)
2) ( 2sinx +1)(3cos4x +2sinx -4) + 4cos^2 x= 3
3) 32cos^6 x - cos6x = 4
4) tan^2 x(1-sin^3 x) + cos^3 x = 0