tính sin^2.10°- sin^2.20°+sin2^2.30° -sin2^40° -sin^2.50 °-sin^2.50°+sin^2.60°-sin^2.70°+sin^2.80°

Giải thích các bước giải:

`sin^2 10^0- sin^2 20^0+sin^2 30^0 -sin^2 40^0 -sin^2 50^0+sin^2 60^0-sin^2 70^0+sin^2 80^0`

$=(\sin^210^0+\sin^280^0)-(\sin^220^0+\sin^270^0)+(\sin^230^0+\sin^260^0)-(\sin^240^0+\sin^250^0)$

$=(\sin^210^0+\cos^210^0)-(\sin^220^0+\cos^220^0)+(\sin^230^0+\cos^230^0)-(\sin^240^0+\cos^250^0)$

`=1-1+1-1=0`