已知0y=cos^x-2sin^x+b修改：y=cos^2（x）-2sin^x+b

已知0y=cos^x-2sin^x+b修改：y=cos^2（x）-2sin^x+b 已知函数f(x) =√3cos(2x-y)-sin(2x-y) (0 已知cos(x-y/2)=-1/9,sin(x/2-y)=2/3,0 已知cos(x-y/2)=-1/9,sin(x/2-y)=2/3,0 y=(sin x + COS x)^2 已知函数y=(sin x+ cos x)(sin x+cos x)+2cos x*cos x ,求它的递减区间语气亲和、态度友好 y=2cos x (sin x+cos x) 已知tan=2,求(cos x+sin x)/(cos x-sin x)+sin^2x 已知A（cos x,sin x）B（cos y,sin y）（cos z,sinz）O为原点.向量OA+K倍向量OB+（2-K）倍向量OC=0（0 y=(cos^2x)/(sinxcosx-sin^2x),(0 已知sinx=3/5,x∈(π/2,π),求【sin(x+y)+sin(x-y)】/【cos（x+y）+cos（x-y）】的值 已知sin(x)+3cos(x)=2,求sin(x)-cos(x)/sin(x)+cos(x)=? sin(x+y)sin(x-y)=k,求cos^2x-cos^2y 问道三角函数题已知sin(x)-sin(y)=-(2/3);cos(x)-cos(y)=(2/3);求cos(x-y) 已知Sin x+Sin y=1/2,Cos x+Cos y=根号3/3,求S求Sin(x-y)/2 已知:tan x=2 求:sin x+cos x/sin x-cos x=? 证明COS（X+Y）COS（X-Y）=COS^2X-SIN^2Y 证明cos(x+y)cos(x-y)= cos^2(x)-sin^2(y)