1) cos26*cos14-cos64*cos76-cos40=cos26*cos14-cos(90-26)*cos(90-14)-cos40=cos26*cos14-sin26*sin14-cos40=cos(26+14)-cos40=cos40-cos40=0;
2) sin50*cos22-sin40*cos68-sin20=sin50*cos22-sin(90-50)*cos(90-22)-sin20=sin50*cos22-cos50*sin22-sin20=sin(50-22)-sin20=sin28-sin20=2cos24*sin4.