Tính A - sin^2 10° + sin^2 20° +..+ sin^2 90°

Tính $\mathrm{A}-{\sin }^{2}10°+{\sin }^{2}20°+...+{\sin }^{2}90°$
         $\mathrm{B}-\tan 10°.\tan 20°.\tan 30°....\tan 80°$