>340

sin(y) = sin(z) より,
 0 = sin(y) - sin(z) = 2sin((y-z)/2)cos((y+z)/2),
sin((y-z)/2) =0 ⇔ (y-z)/2 = nπ,
 cos((y+z)/2) =0 ⇔ (y+z)/2 =(n +1/2)π,