Question

sin(-420).cos(570)+cos(300).sin(-210)

Answer 1

sin(-420°)cos570°+cos300°sin(-210°)
=-sin420°cos570°-cos300°sin210°
=sin{(90°×4)+60°}cos{(90°×6)+30°}-cos{(90°×3)+30°}sin{(90°×2)+30°}
=sin60°(-cos30°)-sin30°(-sin30°)
=(√3/2)(-√3/2)-(1/2)(-1/2)
=3/4+1/4
=(3+1)/4
=1 (Answer)