sin^20+cos^50=sin^30sin^70=

sin^20+cos^50=sin^30sin^70= sin^2(20)-sin^2(25)sin(20)+cos^2(50)+cos^2(25)sin20 为什么sin(?)=cos(?) sin（sin（sin（sin（x）=cos（cos（cos（cos（x）,X等于多少? sin(10°)+sin(20°)cos(50°)求值 求证:sin^2/(sin-cos) - (sin+cos)/(tan^2 -1) =sin+cos sin平方20+cos平方50+sin30sin70=多少? sin^2 20+cos^2 50+sin20cos50=? sin^2 20+cos^2 50+sin20cos50=? sin^2 20+cos^2 50+sin30cos70=? sin^2(20)+cos^2(50)+sin20sin50 sin(50)=m,cos(10)=? sin^2 30°+cos()=1 sin cos sin(50度)*cos(10度)+sin(40度)*sin(10度)= 计算:sin方10°+sin方20°+sin方30°+sin方40°+sin方50°+sin方60°+sin方70°+sin方80°+sin方90°= cos(45+30)cos(45-30)+sin(45+30)sin(45-30=) 证明sin^2(x)+cos^2(x+30)+sin(x)cos(x+30)=3/4