14Jan

Доказать тождество 1-2cos2^a/sinacosa=tga-ctga

иванчикjcnm Алгебра 1 0

Доказать тождество 1-2cos2^a/sinacosa=tga-ctga

Posted by иванчикjcnm | Posted at Jan 14, 2014 | Categories: Алгебра

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CEREDA
CEREDA

[latex] frac{1-2cos^2a}{sinxcdot cosx} =Big [cos^2a= frac{1+cos2a}{2}; ; o ; ; 2cos^2a=1+cos2a; Big ]=\\= frac{1-(1+cos2a)}{sinacdot cosa} = frac{-cos2a}{sinacdot cosa} = frac{-(cos^2a-sin^2a)}{sinacdot cosa} = -frac{cos^2a}{sinacdot cosa} +frac{sin^2a}{sinacdot cosa} =\\ =-frac{cosa}{sina} +frac{sina}{cosa} =-ctga+tga=tga-ctga[/latex]

Jan 14, 2014 15:47

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