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)=
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^2 2。
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 。
答:直接用和差化积公式: 1/2*(cos2B-cos2A) =1/2*{-2sin[(2B+2A)/2]sin[(2B-2A)/2]} =-sin(B+A)sin...详情>>
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