Let,asinx=bsin(x+2π3)=csin(x+4π3)=khence,ka=sinx;kb=sin(x+2π3);kc=sin(x+4π3)⇒kc=sin(2π+(x−2π3))=sin(x−2π3)∴ka+kb+kc=sinx+sin(x+2π3)+sin(x−2π3)⇒k(1a+1b+1c)=sinx+sinxcos2π3+sin2π3cosx+sinxcos2π3−sin2π3cosx⇒k.ab+bc+caabc=sinx+2cos2π3sinx⇒k.ab+bc+caabc=0(∵cos2π3=−12)sincekisnotzero∴ab+bc+caabc=0⇒ab+bc+ca=0