10π/7=π+3π/7
3π/7<3π/6=π/2 =>3π/7<π/2=>
π+3/7*π∈cadran 3.
sin(π+3/7*π)<0 pt ca in cadranul 3sinusul e negativ
b)sin25/24*π=sin(π+π/24) π/24>π/2=>π+π/24 apartine cadranului 3 unde sinusul e negativ
d) sin35π/18=sin(2π-π/18) π/18<π/2=>
2π-π/18 ∈cadran4 unde sinusul e negativ
sin9π=sin(8π+π)=sinπ=-1
