Question

sin 40° cos 10° - sin 10° cos 40°

Answer 1

Sin 40° cos 10° - sin 10° cos 40° =sin(40°-10°)=sin30°=1/2

Answer 2

sinacosb-cosasinb=sin(a-b)
sin40cos10-sin10cos40=sin(40-10)=sin30=1/2