

Cho [tex]0^{\circ}[/tex] <[tex]\alpha[/tex]< [tex]90^{\circ}[/tex] .Biết sin [tex]\alpha =\frac{1}{3}[/tex]. TÍnh g trị biểu thức:
[tex]A= 3(sin^{4}\alpha +cos^{4}\alpha )-2(tan^{2}\alpha +cos^{6}\alpha )+tan^{2}\alpha (2cos^{2}\alpha +sin^{2}\alpha -1)[/tex]
[tex]A= 3(sin^{4}\alpha +cos^{4}\alpha )-2(tan^{2}\alpha +cos^{6}\alpha )+tan^{2}\alpha (2cos^{2}\alpha +sin^{2}\alpha -1)[/tex]
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