$tan ²40^{o}.sin ²50^{o}-3+(1-sin40^{o})(1+sin40^{o})$ $Giúp mk vs!$
2 câu trả lời
$\displaystyle \begin{array}{{>{\displaystyle}l}} \tan^{2} 40.\sin^{2} 50-3+( 1-\sin 40)( 1+\sin 40)\\ =\tan^{2} 40.\cos^{2} 40-3+1-\sin^{2} 40\\ =\sin^{2} 40-2-\sin^{2} 40\\ =-2\ \\ P/s:\ \tan \alpha =\frac{\sin \alpha }{\cos \alpha } \ \Longrightarrow \tan \alpha .\cos \alpha =\sin \alpha \end{array}$
`#huy`
`tan^2 40^0 . sin^2 50^0-3+(1-sin 40^0)(1+sin40^0)`
`=tan^2 40^0 . cos^2 40^0-3+1-sin^2 40^0`
`=sin^2 40^0-2-sin^2 40^0`
`=-2`
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