а) cos(t) < 0,5

cos(t) = 0,5

t = π/3 + 2πn

t = -π/3 + 2πn = 5π/3 + 2πn

cos(t) < 0,5

t € (π/3 + 2πn ; 5π/3 + 2πn) ; n € Z

б) cos(t) >= sqrt(2)/2

cos(t) = sqrt(2)/2

t = π/4 + 2πn

t = -π/4 + 2πn

cos(t) >= sqrt(2)/2

t € [-π/4 + 2πn ; π/4 + 2πn] ; n € Z

в) sin(t) > sqrt(3)/2

sin(t) = sqrt(3)/2

t = π/3 + 2πk

t = 2π/3 + 2πk

sin(t) > sqrt(3)/2

t € (π/3 + 2πk ; 2π/3 + 2πk) ; k € Z

г) sin(t) =< -0,5

sin(t) = -0,5

t = -π/6 + 2πk

t = -5π/6 + 2πk

sin(t) =< -0,5

t € [-5π/6 + 2πk ; -π/6 + 2πk] ; k € Z