Cosα+cos(240град.+α)+cos(240град.-α) = упростить выражение
1)cosα+2cos[(240град.+ α)+(240град.- α)]/2 cos[(240град.+ α)-(240град.- α)]/2 = = cosα + 2 *(cos(240град)* ( cos((2α) / 2) = cosα*(1 - 2*cos(240град) =
cosα*(1 - 2*cos(180 + 60) = cosα*(1+ 2*cos( 60)) = cosα*(1+ 2*(1/2)) = 2cosα