cosa-cosβ=4/5 sina-sinβ=3/5 求cos(a-β)

sina+cosa=7/13则5sina+4cos cosa-cosβ=4/5 sina-sinβ=3/5 求cos(a-β) 1:已知sina+cosa=根2求sina cosa sin(4方)a+cos(4方)的值2:已知:sina+cosa=1/5(0 cosa+cosβ=-4/5 sina+sinβ=3/5 求cos(a-β)的值 -sina/-cos*-sina*cosa 若sina+cosa/sina-cosa=2,则4sin^2a-3sinacosa-5cos^2a= sin(a+kpai)=-2cos(a+kpai),k属于Z求(4sina-2cosa)/(5cosa+3sina) sin(a+kπ)=2cos[a+(k+1)π].求5cosa+3sina/4sina-2cosa sin(a+kπ)=2cos[a+(k+1)π].求5cosa+3sina/4sina-2cosa 已知3sina=—cosa求sina+2cosa/5cosa-sina (2) 1/2sinacosa+cos²a 已知tana=3,求(3sina-2cosa)/(2sina+5cosa) ; cos^2a ; sina*cosa 证明 cosa/(1+sina0-sina/(1+cosa)=2(cosa-sina)/(1+sina+cos)cosa/(1+sina）-sina/(1+cosa)=2(cosa-sina)/(1+sina+cos) 已知sinα=2cosα,求sina+5cosa/-2cosa+sinasina+5cosa/-2cosa+sina 求证道数学题.(cosa-sina)/(1+sina+cosa)=cos/(1+sina)-sina/(1+cosa) sina-cosa=-5/4,则sina.cosa=? 求证[sina(1+sina)+cos(1+cosa)][sina(1-sina)+cos(1-cosa)]=sin2a 已知sina=2cosa.求sina-4cosa/5sina+2cos及sin平方a+2sinacosa的值 已知tanA=3,计算:(4sinA-2cosA)/(5cosA+3sinA)?(sinA-cosA)^2?