Sin2004cos1974- sin1974cos2004=
Sin2004cos1974-sin1974cos2004= ((sin2004-1974)+sin(2004+1974))/2- ((sin(1974-2004) +sin(1974+2004))/2= (sin30)+sin3978-sin(-30)-sin3978)/2= (sin30-Sin(-30))/2=sin30=1/2=0,5.