a)cos40˚-cos10˚ ,
б)sin42˚-sin26˚,
в)cos37˚+cos23˚,
г)sin130˚+sin110˚ ,
д)cos20˚-cos70˚,
е)sin(α+x)-sinα,
ж)cos(α-β)+cos(α+β),
з)cos50˚-sin70˚,
и)sin20˚-cos20˚
cos40-cos10=cos30= √3/2
sin42-sin26= sin16=0.2756
cos37+cos23=cos60=0.5
sin130+sin110=sin140 0.6428
cos20-cos70=-cos50