решите неравенство:

1-4sin^(2)x<0

-4sin^(2)x<-1

sin^(2)x>1/4

(1-cos2x)/2>1/4

1-cos2x>1/2

cos2x<1/2

2x<+(-)arccos1/2+2πn

2x<+(-)π/3+2πn

x<+(-)π/6+πn