sin(20°+α)/cos(70°-α)-tan(50°+α)tan(40°-α)=
问题描述：
sin(20°+α)/cos(70°-α)-tan(50°+α)tan(40°-α)=
要求具体的解法
答
因为 (20°+α)+(70°-α)=90°所以 sin(20°+α)=cos(70°-α) 即sin(20°+α)/cos(70°-α)=1因为 (50°+α)+(40°-α)=90° 所以 tan(40°-α)=cot(50°+α) 所以tan(50°+α)tan(40°-α)=1所以 上式=1-1=0...