sin(540+B)sin(B+810)
(B-это ветта)
(sin540cosB+cos540sinB)(sinBcos810+cosBsin810)=(sin(360+180)cosB+cos(360+180)sinB)(sinBcos(720+90)+cosBsin(720+90)=(sin180cosB+cos180sinB)(sinBcos90+sin90cosB)=(0*cosB-1sinB)(sinB*0+1cosB)= -sinB*cosB