Tính sin²10°+sin²20°+sin²30°+sin²80°+sin²70°+sin²60° 23/08/2021 Bởi Eden Tính sin²10°+sin²20°+sin²30°+sin²80°+sin²70°+sin²60°
`sin^2 10^0+sin^2 20^0+sin^2 30^0+sin^2 80^0+sin^2 70^0+sin^2 60^0` `=cos^2 80^0 +cos^2 70^0 + cos^2 60^0+sin^2 80^0 +sin ^2 70^0 +sin^2 60^0 ` `=(cos^2 80^0+sin^2 80^0)+(cos^2 70^0+sin^2 70^0)+(cos^2 60^0+sin^2 60^0)` `=1+1+1` `=3` Bình luận
$\sin^210^o+\sin^280^o+\sin^220^o+\sin^270^o+\sin^230^o+\sin^260^o$ $= \sin^210^o+\cos^220^o+\sin^220^o+\cos^220^o+\sin^230^o+\cos^230^o$ $= 1+1+1$ $=3$ Bình luận
`sin^2 10^0+sin^2 20^0+sin^2 30^0+sin^2 80^0+sin^2 70^0+sin^2 60^0`
`=cos^2 80^0 +cos^2 70^0 + cos^2 60^0+sin^2 80^0 +sin ^2 70^0 +sin^2 60^0 `
`=(cos^2 80^0+sin^2 80^0)+(cos^2 70^0+sin^2 70^0)+(cos^2 60^0+sin^2 60^0)`
`=1+1+1`
`=3`
$\sin^210^o+\sin^280^o+\sin^220^o+\sin^270^o+\sin^230^o+\sin^260^o$
$= \sin^210^o+\cos^220^o+\sin^220^o+\cos^220^o+\sin^230^o+\cos^230^o$
$= 1+1+1$
$=3$