Giải phương trình: 2cos^2(x - π/3) - 3sin(x - π/3) = 0

a) 2cos^2(x-π/3)-3sin(x-π/3)=0
b) 3sin^2(π/4-x)-2cos(π/4-x)+2=0
c) 2cos4x-4cos2x=1
d) cos6x-5sin3x-3=0
e) cos(2x+π/3)-4cos(x+π/6)+5/2=0
f) 6sin^2x+cos2x+cosx=0