2sin^2asin^2b 2cos^2acos^2b-cos2acos^b化简

2sin^2asin^2b+2cos^2acos^2b-cos2acos^b化简2.题设函数y=x方-4px的图像经过M(tana,1),N(tanb,1)求tan(a+b)=

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第1小题题目后面不清？2sin^2asin^2b+2cos^2acos^2b-cos2acos^b化简2(sinA^2)sinB^2+2(cosA^2)cosB^2-cos2AcosB^2=2(sinA^2)sinB^2+(2cosA^2-cos2A)cosB^2=2(sinA^2)sinB^2+[2cosA^2-(2cosA^2-1)]cosB^2=2(sinA^2)sinB^2+cosB^2=2(sinA^2)sinB^2+1-sinB^2=(2sinA^2-1)sinB^2+1=-cos2AsinB^2+1=1-cos2AsinB^22。依题意，tgA,tgB是方程x^2-4px=1的两个根，且tgA≠tgB∵由韦达定理得：tgA+tgB=4p，tgA*tgB=-1∴tg(A+b)=(tgA+tgB)/(1-tgA*tgB)=4p/(1+1)=2p。