The value of ${\cos }^{2}10°-\cos 10°\cos 50°+{\cos }^{2}50°$

We know that  if $A\pm B={60}^0$ then ${\cos }^{2}A-\cos A\cos B+{\cos }^{2}B=\raisebox{1ex}{$3$}\!\left/ \!\raisebox{-1ex}{$4$}\right.$

So here $A={10}^0,B={50}^0$

${\cos }^2{10}^0-\cos {10}^0\cos {50}^0+{\cos }^2{50}^0=\raisebox{1ex}{$3$}\!\left/ \!\raisebox{-1ex}{$4$}\right.$