证sin^2a x tana+cos^2a x cota+2sinacosa=1/sinacosa
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证sin^2a x tana+cos^2a x cota+2sinacosa=1/sinacosa
证sin^2a x tana+cos^2a x cota+2sinacosa=1/sinacosa
证sin^2a x tana+cos^2a x cota+2sinacosa=1/sinacosa
sin^2a x tana+cos^2a x cota+2sinacosa
=sin³a/cosa+cos³a/sina+2sinacosa
=(sin^4a+cos^4a+2sin²acos²a)/sinacosa
=(sin²a+cos²a)²/sinacosa
=1/sinacosa
得证
sin^2a x tana+cos^2a x cota+2sinacosa
=(1-cos^2a)sina/cosa+(1-sin^2a )cosa/sina+2sina cosa
=sina/cosa-cos^2a*sina/cosa+cosa/sina-sin^2a*cosa/sina+2sina cosa
=sina/cosa+cosa/sina-cosa*sina-...
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sin^2a x tana+cos^2a x cota+2sinacosa
=(1-cos^2a)sina/cosa+(1-sin^2a )cosa/sina+2sina cosa
=sina/cosa-cos^2a*sina/cosa+cosa/sina-sin^2a*cosa/sina+2sina cosa
=sina/cosa+cosa/sina-cosa*sina-sina*cosa+2sina cosa
=sina/cosa+cosa/sina
=sin^2a/(sina cosa)+cos^2a/(sina cosa)
=(sin^2a+cos^2a)/(sina cosa)
=1/(sina cosa)
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