theorem :: NIVEN:69

for r being Real
for i being Integer st ((3 * PI) / 2) + ((2 * PI) * i) <= r & r <= (2 * PI) + ((2 * PI) * i) & r / PI is rational & sin r is rational holds
r in {(((3 * PI) / 2) + ((2 * PI) * i)),(((11 * PI) / 6) + ((2 * PI) * i)),((2 * PI) + ((2 * PI) * i))}