Giải phương trình: √3tan^2x - (3 + √3)tanx + 3 = 0; sin^2x - 3cosx - 4 = 0

a) √3tan^2x-(3+√3)tanx+3=0
b) Sin^2x-3cosx-4=0
c) (√3-1)sinx-(√3+1)cosx+√3-1=0
d) Tan^2x+2tanx+1=0
e) Cos^22x+cosx2x-3/4=0
f) Sinx+√3cosx=2
g) Sin^2x-2sinx=0
h) 2sin^2-3sinx+1=0
i) 2sin^2x+5sinx-3=0