已知sinα-cosα=-1/5且α属于(0,π)
1-2sinacosa=1/2524/25=2sinacosa,sin2a=24/25>0据题意,00,cosa>0,sina cosa>01 2sinacosa=(sina cosa)^2=49/25sina cosa=7/550tana=24 24tan^2a12tan^2a-25tana 12=0tana=4/3,cos^2a=1/(1 16/9)=9/25,cosa=3/51、sin^2a-cos^2a=(sina-cosa)(sina cosa)=(-1/5)*(7/5)=-7/252、tana cosa=4/3 3/5=(20 9)/15 =29/153、tan...全部
1-2sinacosa=1/2524/25=2sinacosa,sin2a=24/25>0据题意,00,cosa>0,sina cosa>01 2sinacosa=(sina cosa)^2=49/25sina cosa=7/550tana=24 24tan^2a12tan^2a-25tana 12=0tana=4/3,cos^2a=1/(1 16/9)=9/25,cosa=3/51、sin^2a-cos^2a=(sina-cosa)(sina cosa)=(-1/5)*(7/5)=-7/252、tana cosa=4/3 3/5=(20 9)/15 =29/153、tana=4/3。
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